Preventive Medicine 67 (2014) 112–118
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Self-rated health and mortality in a prospective Chinese elderly cohort study in Hong Kong Chen Shen a, C. Mary Schooling a,c,⁎, Wai Man Chan b, Jiang Xiu Zhou a, Janice M. Johnston a, Siu Yin Lee b, Tai Hing Lam a a b c
School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China Department of Health, Hong Kong SAR, China School of Public Health, The City University of New York and Hunter College, NY, USA
a r t i c l e
i n f o
Available online 18 July 2014 Keywords: Aging Cohort study Mortality Self-rated health
a b s t r a c t Objectives. In the West, self-rated health reliably predicts death, but conceptualizations of health and causecomposition of mortality may be contextually specific. Little is known as to how self-rated health predicts death in non-Western settings. Methods. Multivariable Cox regression analysis was used to assess the adjusted associations of age-comparative and self-comparative self-rated health with death from all- and specific-causes using a population-based cohort of 66,820 Chinese (65+ years) enrolled from 1998 to 2001 at 18 Elderly Health Centers in Hong Kong, and followed until May 31, 2012. Results. During an average of 10.9 years follow-up, 19,845 deaths occurred with 6336 from cancer. Worse age-comparative self-rated health, compared with better, was positively associated with death from all-causes (hazard ratio 1.68, 95% confidence interval 1.59, 1.77), cardiovascular disease (hazard ratio 1.83, 95% confidence interval 1.66, 2.02), stroke (hazard ratio 1.93, 95% confidence interval 1.63, 2.29), ischemic heart disease (hazard ratio 1.77, 95% confidence interval 1.51, 2.08), cancer (hazard ratio 1.17, 95% confidence interval 1.06, 1.30) and respiratory disease (hazard ratio 2.25, 95% confidence interval 2.01, 2.52), adjusted for age and sex. Selfcomparative self-rated health was not associated with higher mortality. Conclusion. Age-comparative self-rated health predicted death in older people from a non-Western setting although the association was less marked than in Western settings. © 2014 Elsevier Inc. All rights reserved.
Introduction Self-rated health (SRH), a subjective assessment of health status, is a powerful predictor of mortality in older persons. SRH is as an important health indicator which is easy to measure and provides a good reflection of health status (de Bruin et al., 1996). SRH may be assessed as global SRH using questions such as “What do you think of your health in general?” (Eriksson et al., 2001; Idler and Benyamini, 1997) or as comparative SRH, including age-comparative SRH (comparing oneself to other people of the same age) and self-comparative SRH (comparing oneself to one's own status a year earlier) (Alfonso et al., 2012; Fernández-Ruiz et al., 2013). In the West, measurement methods for SRH such as type of scale, wording of the question and number of
Abbreviations: BMI, body mass index; CI, confidence interval; EHC, elderly health center; GDS, Geriatric Depression Scale; HR, hazard ratio; ICD, International Classification of Disease; IHD, ischemic heart disease; RRR, relative risk ratio; SRH, self-rated health. ⁎ Corresponding author at: School of Public Health at Hunter College, The City University of New York, 2180 Third Avenue, New York, NY 10035, USA. E-mail address: [email protected] (C.M. Schooling).
http://dx.doi.org/10.1016/j.ypmed.2014.07.018 0091-7435/© 2014 Elsevier Inc. All rights reserved.
options differ; both global and age-comparative SRH predict death (Fernández-Ruiz et al., 2013; Lima-Costa et al., 2012; Young et al., 2010) although comparisons are not always consistent. Sargent-Cox et al. (2010) reported that global SRH was a better predictor of allcause mortality than age-comparative SRH while Fernández-Ruiz et al. (2013) reported that age-comparative SRH was better. However, selfcomparative SRH is a weaker predictor of mortality (Bath, 2003; Fernández-Ruiz et al., 2013). The magnitude of association of SRH with mortality may vary by cause of death. SRH might be more strongly associated with diseases with a prolonged course and substantial impact on daily life, such as cardiovascular and respiratory diseases, than diseases without notable signs in the early stages which then develop rapidly such as cancer (Fernández-Ruiz et al., 2013). SRH is easy to measure, and could be a health indicator for older people given it might reveal health status before symptoms develop. Most studies of the association of SRH with mortality relate to Western populations, where associations may vary by socioeconomic position (Burström and Fredlund, 2001; Huisman et al., 2007; Møller et al., 1996; Mossey and Shapiro, 1982). However, these observations may not generalize to other settings because of contextually-specific
C. Shen et al. / Preventive Medicine 67 (2014) 112–118
cause-composition of mortality, culturally-specific perceptions of health and varying social patterning of health-related attributes. In the West, cardiovascular disease is the leading cause of death, but cancer is the leading cause of death in Hong Kong (Lozano et al., 2013). Moreover, self-ratings tend to be optimistic in the West (Heistaro et al., 2001; Montlahuc et al., 2011) but other cultures may favor moderation, such as the Chinese “doctrine of the mean” (Leung, 2010; Li et al., 2004; Moore, 1967) which may make people rate their health as “normal”. Finally, socioeconomic patterning may be less entrenched in settings where economic development is recent (Maddison, 2007) and socioeconomic disadvantage has not been perpetuated over generations. Few studies have addressed the association of SRH with mortality in non-Western settings, often with short follow-up and small samples (Ho, 1991; Leung et al., 1997). We have previously reported that agecomparative SRH was more strongly associated with concurrent physical conditions than self-comparative SRH (Li et al., 2006) as well as that depression was associated with SRH and mortality (Sun et al., 2013). Here, we examined the role of SRH in predicting death from all- and specific causes in a developed non-Western setting, where cardiovascular disease is not the leading cause of death (Lozano et al., 2013), cultural preferences emphasize moderation (Leung, 2010; Moore, 1967) and universal education is recent (Johnson, 1998). We also examined whether any associations varied by socioeconomic position. Methods Source of data Since July 1998, eighteen Elderly Health Centers (EHC) have been established by the Hong Kong Government Department of Health to offer older people screening services and medical examinations, aiming to enhance primary health care by improving self-care ability, encouraging healthy living and strengthening social integration. All residents of Hong Kong aged ≥65 years were encouraged to enroll for a small annual fee of HK$110 (US$1 = HK$7.8; waived for those on public social security assistance). This cohort study covered all 66,820 enrollees from July 1998 to December 2001. More women were enrolled than men (44,140 versus 22,680); otherwise, age, socioeconomic position, current smoking status and hospital use were similar to the general older population (Schooling et al., 2006; Xu et al., 2013). Nurses and doctors conducted health assessments, using standardized structured interviews, and comprehensive clinical examinations. Information on demographic characteristics, socioeconomic position, lifestyle, and disease history was collected, as described elsewhere (Schooling et al., 2006; Xu et al., 2013). Ethics approval was obtained from The University of Hong Kong–Hospital Authority Hong Kong West Cluster Joint Institutional Review Board. Measures
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of health services (2 items: regular use of medication and any hospital admission in the last year), frailty (3 items: cognitive impairment, functional impairment and two or more falls in the last 6 months), and unintentional weight loss of more than 4.5 kg in the last 6 months (Schooling et al., 2006). The Kunder–Richardson-20 coefficient which was used to determine the internal consistency of the index with dichotomous responses was 0.44. Follow-up Vital status was ascertained by record linkage to death registration in Hong Kong on unique Hong Kong identity card number. The last date of follow-up or censor date for living participants was May 31, 2012. Most participants in the EHC cohort remain in Hong Kong, any deaths outside Hong Kong are also usually registered in Hong Kong. Where vital status could not be ascertained from death registration or record linkage to use of routine services, regular telephone interviews were conducted in 2004, 2006 and 2009 to obtain vital status and cause of death. Causes of death were routinely coded by International Classification of Diseases (ICD) 9th Reversion before 2001 and 10th Reversion after 2001 and checked by the Department of Health. Most Hong Kong residents died in hospital, ensuring accurate ascertainment of cause of death, which we have used in previous studies (Schooling et al., 2006; Xu et al., 2013). Those whose vital status could not be determined were assumed to be alive. The outcomes were death from all-causes, cardiovascular disease (ICD9 401–459 or ICD10 I10–I99), ischemic heart disease (IHD) (ICD9 410–414 or ICD10 I20–I25), stroke (ICD9 430–438 or ICD10 I60–I69), cancer (ICD9 140–239 or ICD10 C00–C97, D00–D48) and respiratory disease (ICD9 460–519 or ICD10 J00–J99). Statistical analysis Chi-square tests were used to compare baseline characteristics by age- and self-comparative SRH. Multivariable Cox regression was used to estimate adjusted hazard ratios (HR) with 95% confidence intervals (CI) for death from all- and specific causes. The proportional hazards assumption was checked by visual inspection of plots of log (− log S) against time, where S is the estimated survival function. Models were built in stages. Model 1 adjusted for age and sex. Model 2 additionally adjusted for socioeconomic position (education, monthly expenditure and housing type), lifestyle (alcohol use, smoking and exercise), body mass index (BMI) and depression as Geriatric Depression Scale (GDS) score ≥ 8. Model 3 additionally adjusted for objective health status. Whether associations varied by sex, age or socioeconomic position was assessed from the significance of interaction terms and the heterogeneity of estimates across strata. We repeated the analysis by follow-up duration including short-term (b 5 years) and long-term (excluding all deaths within first 5 years). We used the relative risk ratio (RRR) to assess differences in these associations (Altman and Bland, 2003).
SRH was assessed at baseline from two verbal questions: (1) How would you rate your health condition compared with others of your age? (age-comparative SRH) (2) How would you rate your health condition this year compared with last year? (self-comparative SRH) Both questions had three response options: better, normal and worse. Objective health status Several morbidity, comorbidity, or prognostic indices for older people exist, but not for Asians in a primary care setting. We used our previously constructed, simple but comprehensive 11-item index by counting chronic conditions (5 items: heart disease, stroke, diabetes, chronic obstructive pulmonary disease and/or asthma, and hypertension), use
Results Among 66,820 participants (22,680 men and 44,140 women) enrolled at baseline from 1998 to 2001, 66,814 (99.9%) with age- and self-comparative SRH were included here. Of 66,820 participants, 62,824 had vital status ascertained from record linkage including 19,452 deaths, 2539 had vital status obtained by telephone interview including 393 deaths, and 1457 had unknown vital status and were presumed to be alive. The mean follow-up was 10.9 years (standard deviation = 3.1). Of the 19,845 deaths, 6336 were from cancer (31.9%), 5651 from cardiovascular disease and 4060 from respiratory disease. Most people had better or normal age-comparative SRH (92.3%) but normal or worse self-comparative SRH (93.6%). Table 1 shows baseline characteristics by age- and self-comparative SRH for men and women. Women were more likely to report worse age- and self-comparative
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Table 1 Baseline characteristics by age- and self-comparative SRH in 66,814 older people enrolled at EHCs in Hong Kong from 1998 to 2001. Age-comparative SRH
Self-comparative SRH
Men (n = 22,678)
Age group (%)
Education (%)
Housing type (%)
Alcohol (%)
Smoking (%)
Exercise (%)
BMI (%)
GDS score (%) Health status (%)
Men (n = 22,678)
Women (n = 44,136)
Better (n = 6739)
Normal (n = 14740)
Worse (n = 1199)
Better (n = 9125)
Normal (n = 31067)
Worse (n = 3944)
Better (n = 1464)
Normal (n = 14039)
Worse (n = 7175)
Better (n = 2821)
Normal (n = 25329)
Worse (n = 15986)
67.5 29.4 3.1 36.3 49.8 8.6 5.3 22.9 27.5 37.5 12.1 55.8 38.5 5.7 46.9 16.9 25.2 11.0 38.4 20.1 41.6 14.8 25.3 59.9 4.7 33.3 24.3 37.7 94.9 5.1 17.0 29.1 21.5 19.0 13.4
70.9 26.3 2.8 28.7 51.9 11.5 8.0 19.5 34.3 35.2 11.1 55.4 39.3 5.3 49.6 18.0 23.2 9.2 38.3 20.5 41.2 17.1 24.1 58.8 5.7 33.5 24.5 36.3 93.5 6.5 15.3 24.8 21.9 21.6 16.4
68.2 28.7 3.1 25.3 52.2 11.4 11.1 18.2 29.6 36.5 15.7 46.3 45.8 7.9 49.9 26.0 16.3 7.9 31.6 22.9 45.6 22.7 27.3 50.0 14.0 34.6 20.1 31.3 74.5 25.5 5.4 14.6 20.0 22.4 37.7
67.1 28.3 4.7 13.8 31.1 19.4 35.7 16.5 27.3 39.5 16.6 53.4 38.9 7.7 82.1 5.7 11.0 1.2 87.1 4.2 8.7 13.1 28.3 58.6 4.2 31.5 22.2 42.1 93.7 6.3 15.8 29.6 21.1 19.2 14.2
69.3 27.0 3.7 9.4 29.1 20.7 40.8 13.5 31.0 39.5 16.0 53.0 39.6 7.3 85.1 5.3 8.7 1.0 88.8 3.9 7.3 14.8 27.6 57.7 5.0 30.7 21.9 42.4 90.2 9.8 13.5 24.8 21.7 21.6 18.4
67.4 28.4 4.2 7.7 25.9 19.7 46.8 16.1 26.2 37.8 19.9 48.9 44.9 6.2 84.4 8.1 6.7 0.8 86.7 4.0 9.4 17.8 30.2 52.0 7.4 31.5 19.4 41.6 69.4 30.6 7.2 16.8 19.7 23.3 33.0
70.1 27.1 2.8 32.0 49.3 11.3 7.4 20.7 31.5 35.4 12.4 54.4 37.8 7.8 48.9 22.8 19.3 9.0 34.5 17.7 47.8 12.8 22.5 64.7 6.4 33.0 26.3 34.3 95.1 4.9 11.3 24.6 21.1 22.2 20.9
71.8 25.7 2.5 31.4 51.5 10.3 6.8 20.5 32.8 35.5 11.2 55.9 38.7 5.4 49.9 16.1 24.1 10.0 41.0 19.1 39.9 16.0 23.9 60.1 4.9 32.6 25.0 37.4 95.8 4.2 17.3 27.2 21.7 20.3 13.5
65.8 30.5 3.7 29.3 51.3 11.1 8.3 20.5 30.5 36.9 12.2 53.5 41.1 5.4 46.7 21.0 23.1 9.2 32.8 23.7 43.5 18.8 26.5 54.7 7.6 35.4 22.1 35.0 86.9 13.1 12.2 22.4 21.9 21.6 22.0
70.4 26.2 3.4 10.6 27.1 20.5 41.8 17.1 28.5 38.1 16.3 50.4 40.4 9.2 82.7 7.6 8.9 0.9 86.5 3.8 9.6 11.2 29.0 59.8 5.2 30.5 21.3 43.1 91.2 8.8 10.2 25.4 21.3 21.7 21.3
70.6 25.6 3.8 10.4 29.9 20.3 39.4 13.6 31.1 39.7 15.7 53.6 38.8 7.6 85.2 4.7 9.0 1.1 89.5 3.7 6.9 14.2 27.2 58.6 4.7 31.0 22.1 42.2 93.4 6.6 15.2 26.9 21.4 20.9 15.6
65.4 30.4 4.2 9.7 28.6 20.3 41.5 15.1 28.0 39.1 17.8 51.8 41.8 6.5 83.6 6.7 8.9 0.9 86.7 4.5 8.7 16.0 29.0 55.0 5.7 31.0 21.1 42.2 81.8 18.2 11.2 22.1 21.5 21.8 23.4
Two-sided p value from a χ2 test between SRH and baseline characteristics: all b0.05.
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Monthly expenditure (%)
65–74 75–84 ≥85 Secondary above Primary No formal but literate Illiterate ≥3000HK$ 2000–2999HK$ 1000–1999HK$ b1000HK$ Private Public or aided Temporary or others Never drinker Ex-drinker Social drinker Regular drinker Never smoker Current smoker Ex-smoker Never b30 min/day ≥30 min/day b18.5 18.5– b 23 23– b 25 ≥25 b8 ≥8 0 1 2 3 4 or more
Women (n = 44,136)
C. Shen et al. / Preventive Medicine 67 (2014) 112–118
SRH than men (p values b 0.01). Compared with better age- and selfcomparative SRH, participants with worse age- and self-comparative SRH had lower socioeconomic position, and were more likely to be ever smokers, physically inactive, underweight and to have depression (all p values b 0.05). Age-comparative SRH had a graded association with objective health status but self-comparative SRH had a U-shaped association with objective health status. Participants with normal selfcomparative SRH had the best objective health status. Table 2 shows that compared with better age-comparative SRH, both normal and worse age-comparative SRH were associated with a higher risk of death from all-causes, cardiovascular disease and respiratory disease, but only weakly associated with death from cancer, adjusted for age, sex, socioeconomic position, lifestyle, BMI, depression and objective health status. The association of age-comparative SRH with death from all-causes attenuated substantially after adjusting for objective health status. Discrimination ability from the C statistic was 0.704 (95% CI 0.701, 0.708) for model 2 and 0.722 (95% CI 0.718, 0.726) for model 3. Relative to better self-comparative SRH, normal selfcomparative SRH was associated with a lower risk of death from allcauses, cardiovascular disease, respiratory disease and cancer after similar adjustment. Worse self-comparative SRH was also associated with a lower risk of death from all-cause and cardiovascular disease, but not associated with death from cancer or respiratory disease. The association of self-comparative SRH with death from all- and specific causes did not vary with age-comparative SRH (all p values N 0.05). The association of age-comparative SRH with death from cardiovascular disease and stroke varied by sex (p values for interaction 0.04 and 0.004, respectively). Table 3 shows sex-specific analysis of ageand self-comparative SRH with death from all- and specific causes.
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Men with worse age-comparative SRH had a higher relative ratio of death from cardiovascular disease (RRR = 1.27, 95% CI 1.02, 1.57) and stroke (RRR = 1.76, 95% CI 1.22, 2.54) than women. The association of age- and self-comparative SRH with all-cause mortality varied by age (p values for interaction 0.03 and 0.03, respectively). The association of worse age-comparative SRH with all-cause mortality was weaker in the participants aged ≥ 85, as shown in Table 4. The associations of worse self-comparative SRH with death from all- and specific-causes were similar across different age groups, but the associations of normal self-comparative SRH with all- and specific-causes were stronger among younger age groups. The associations of SRH with death from all- and specific-causes did not vary by socioeconomic position or objective health status (all p values N 0.05). The pattern of associations of SRH with death was similar when stratified by follow-up duration. The magnitude of association of worse age-comparative SRH with all-cause mortality was stronger in the short-term than the long-term (RRR = 1.13, 95% CI 1.01, 1.28), adjusted for age, sex, socioeconomic position, lifestyle, BMI, depression and objective health status. The magnitude of association of worse selfcomparative SRH with all-cause mortality was similar in the short- and long-term (RRR = 0.97, 95% CI 0.86, 1.09). Discussion In this understudied non-Western population, age-comparative SRH predicted death in older people after adjusting for age, sex, socioeconomic position, lifestyle, BMI, depression and objective health status, indicating that age-comparative SRH may act as a proxy of unmeasured signs or symptoms of diseases as age-comparative SRH was also
Table 2 Adjusted associations of age- and self-comparative SRH with death from all- and specific causes in 66,814 older people enrolled at EHCs in Hong Kong from 1998 to 2001 and followed up until May 31, 2012. Age-comparative SRH
All-causes Model 1 Model 2 Model 3 All cardiovascular disease Model 1 Model 2 Model 3 Stroke Model 1 Model 2 Model 3 IHD Model 1 Model 2 Model 3 Other cardiovascular disease Model 1 Model 2 Model 3 All cancer Model 1 Model 2 Model 3 All respiratory disease Model 1 Model 2 Model 3 Other diseases Model 1 Model 2 Model 3
Self-comparative SRH
Better
Normal
Worse
Better
HR
HR
95% CI
HR
Normal
95% CI
HR
HR
95% CI
HR
1 1 1
1.14 1.10 1.06
1.10, 1.18 1.06, 1.14 1.02, 1.09
1 1 1
1.21 1.17 1.11
1 1 1
95% CI
1.68 1.45 1.24
1.59, 1.77 1.37, 1.53 1.17, 1.31
1 1 1
0.78 0.81 0.86
0.74, 0.83 0.77, 0.86 0.81, 0.91
0.94 0.92 0.91
0.89, 1.01 0.87, 0.97 0.86, 0.96
1.13, 1.29 1.10, 1.25 1.04, 1.18
1.83 1.63 1.28
1.66, 2.02 1.47, 1.80 1.15, 1.42
1 1 1
0.75 0.78 0.85
0.68, 0.83 0.70, 0.86 0.77, 0.94
0.87 0.86 0.84
0.79, 0.97 0.77, 0.96 0.76, 0.94
1.26 1.22 1.15
1.13, 1.42 1.09, 1.36 1.03, 1.29
1.93 1.68 1.34
1.63, 2.29 1.41, 2.00 1.13, 1.61
1 1 1
0.75 0.77 0.83
0.63, 0.89 0.65, 0.92 0.70, 0.99
0.92 0.89 0.88
0.77, 1.11 0.75, 1.07 0.73, 1.05
1 1 1
1.15 1.12 1.04
1.04, 1.27 1.01, 1.24 0.94, 1.16
1.77 1.58 1.21
1.51, 2.08 1.34, 1.87 1.02, 1.42
1 1 1
0.76 0.79 0.88
0.65, 0.90 0.67, 0.94 0.74, 1.03
0.87 0.85 0.84
0.73, 1.02 0.72, 1.01 0.71, 0.99
1 1 1
1.24 1.21 1.14
1.09, 1.41 1.06, 1.37 1.00, 1.29
1.79 1.64 1.30
1.48, 2.18 1.34, 2.00 1.07, 1.59
1 1 1
0.74 0.77 0.84
0.61, 0.90 0.64, 0.94 0.69, 1.02
0.83 0.83 0.81
0.68, 1.01 0.68, 1.01 0.66, 0.99
1 1 1
0.99 0.97 0.97
0.93, 1.05 0.92, 1.03 0.91, 1.02
1.17 1.09 1.05
1.06, 1.30 0.98, 1.21 0.95, 1.17
1 1 1
0.87 0.89 0.90
0.79, 0.96 0.80, 0.98 0.81, 0.99
1.00 0.97 0.97
0.90, 1.11 0.88, 1.08 0.87, 1.08
1 1 1
1.27 1.20 1.14
1.17, 1.37 1.11, 1.29 1.06, 1.23
2.25 1.71 1.45
2.01, 2.52 1.52, 1.93 1.28, 1.63
1 1 1
0.75 0.79 0.85
0.66, 0.85 0.70, 0.90 0.75, 0.96
0.98 0.95 0.93
0.87, 1.11 0.83, 1.07 0.82, 1.06
1 1 1
1.20 1.14 1.08
1.11, 1.30 1.05, 1.23 1.00, 1.17
1.89 1.58 1.29
1.68, 2.13 1.39, 1.79 1.14, 1.46
1 1 1
0.72 0.75 0.81
0.64, 0.82 0.66, 0.85 0.71, 0.92
0.91 0.89 0.87
0.80, 1.03 0.78, 1.01 0.77, 0.99
Model 1: adjusted for age group and sex. Model 2: adjusted for age group, sex, education, monthly expenditure, housing type, alcohol use, smoking, exercise, BMI and depression. Model 3: additionally adjusted for objective health status.
Worse
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Table 3 Sex-specific adjusteda associations of age- and self-comparative SRH with death from all- and specific causes in 66,814 older people enrolled at EHCs in Hong Kong from 1998 to 2001 and followed up until May 31, 2012. Age-comparative SRH
Sex Men
Women
a
All-causes All cardiovascular disease Stroke IHD Other cardiovascular disease All cancer All respiratory disease Other diseases All-causes All cardiovascular disease Stroke IHD Other cardiovascular disease All cancer All respiratory disease Other diseases
Self-comparative SRH
Better
Normal
Worse
Better
Normal
Worse
HR
HR
95% CI
HR
95% CI
HR
HR
95% CI
HR
95% CI
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1.03 1.10 1.16 1.01 1.18 0.93 1.11 1.07 1.08 1.11 1.15 1.07 1.10 1.00 1.18 1.10
0.99, 1.09 1.00, 1.21 0.98, 1.38 0.87, 1.18 0.97, 1.44 0.86, 1.01 1.00, 1.23 0.95, 1.20 1.03, 1.13 1.01, 1.21 0.98, 1.33 0.93, 1.24 0.93, 1.30 0.92, 1.09 1.05, 1.33 0.98, 1.22
1.22 1.52 1.97 1.30 1.35 0.94 1.46 1.03 1.26 1.20 1.12 1.19 1.28 1.13 1.46 1.42
1.12, 1.34 1.28, 1.81 1.48, 2.62 0.98, 1.71 0.92, 1.97 0.79, 1.13 1.23, 1.73 0.82, 1.30 1.17, 1.35 1.05, 1.36 0.89, 1.41 0.97, 1.47 1.01, 1.64 0.99, 1.29 1.23, 1.73 1.21, 1.65
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
0.84 0.78 0.69 0.83 0.81 0.82 0.93 0.86 0.87 0.90 0.94 0.90 0.85 0.98 0.79 0.78
0.77, 0.91 0.66, 0.91 0.53, 0.91 0.65, 1.07 0.58, 1.12 0.71, 0.94 0.78, 1.11 0.70, 1.06 0.81, 0.94 0.79, 1.02 0.74, 1.18 0.73, 1.12 0.66, 1.08 0.85, 1.12 0.66, 0.94 0.67, 0.92
0.93 0.83 0.83 0.83 0.82 0.88 1.07 0.99 0.90 0.86 0.91 0.85 0.81 1.06 0.83 0.81
0.85, 1.01 0.70, 0.98 0.63, 1.11 0.64, 1.08 0.58, 1.15 0.75, 1.02 0.89, 1.29 0.80, 1.23 0.83, 0.97 0.75, 0.98 0.72, 1.16 0.68, 1.06 0.63, 1.04 0.92, 1.23 0.69, 0.99 0.69, 0.95
Adjusted for age group, education, monthly expenditure, housing type, alcohol use, smoking, exercise, BMI, depression and objective health status.
strongly related to objective health status. The association was stronger for death from cardiovascular disease and respiratory disease than for death from cancer. Men with worse age-comparative SRH had a higher relative ratio of death from cardiovascular disease and stroke than women. The association of worse age-comparative SRH with all-cause mortality was stronger in younger age groups and in the short-term. The associations of age-comparative SRH with death from all- and specific causes did not differ by socioeconomic position. In contrast, worse self-comparative SRH did not predict higher mortality, and the results did not differ by sex, socioeconomic position, follow-up duration, cause of death or age-comparative SRH. Despite using a large prospective cohort with long term follow-up, this study has limitations. First, SRH was assessed at baseline, but may change with age. However, SRH is stable over time, even after major
medical events (Cotter and Lachman, 2010; Wilcox et al., 1996). Second, global SRH is not available, so we cannot assess whether global or comparative SRH predicts death better. Third, participants might be healthier than the general older population because the EHC may attract older people who are ambulatory and more health conscious. However, the associations of age- and self-comparative SRH with death did not vary with health status. Fourth, objective health status was defined based on self-report with relatively low internal consistency perhaps because this index is an overall assessment of health status with independent items. However, this health status index has a clear graded association with death in this cohort (Schooling et al., 2006), suggesting its validity. Although we cannot rule out recall bias, the use of simple yes/no questions in assessing chronic conditions might minimize recall error. Fifth, we did not have information on the health care participants
Table 4 Age-specific adjusteda associations of age- and self-comparative SRH with death from all- and specific causes in 66,814 older people enrolled at EHCs in Hong Kong from 1998 to 2001 and followed up until May 31, 2012. Age-comparative SRH
Age group 65–74
75–84
≥85
a
All-causes All cardiovascular disease Stroke IHD Other cardiovascular disease All cancer All respiratory disease Other diseases All-causes All cardiovascular disease Stroke IHD Other cardiovascular disease All cancer All respiratory disease Other diseases All-causes All cardiovascular disease Stroke IHD Other cardiovascular disease All cancer All respiratory disease Other diseases
Self-comparative SRH
Better
Normal
Worse
Better
Normal
Worse
HR
HR
95% CI
HR
95% CI
HR
HR
95% CI
HR
95% CI
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1.07 1.16 1.22 1.15 1.12 0.92 1.34 1.15 1.09 1.14 1.21 1.08 1.16 1.00 1.16 1.09 1.04 0.96 0.93 0.78 1.40 1.38 0.97 1.02
1.02, 1.13 1.05, 1.29 1.02, 1.45 0.97, 1.35 0.91, 1.38 0.85, 1.00 1.16, 1.54 1.01, 1.30 1.04, 1.15 1.04, 1.26 1.02, 1.44 0.92, 1.25 0.97, 1.39 0.91, 1.11 1.04, 1.29 0.97, 1.22 0.93, 1.15 0.79, 1.17 0.66, 1.31 0.57, 1.06 0.94, 2.09 1.05, 1.81 0.80, 1.18 0.81, 1.28
1.35 1.38 1.52 1.34 1.27 1.05 2.18 1.41 1.30 1.36 1.40 1.31 1.38 1.11 1.37 1.40 0.96 1.11 1.03 0.88 1.73 1.02 0.82 0.91
1.25, 1.47 1.18, 1.62 1.17, 1.97 1.04, 1.72 0.92, 1.75 0.92, 1.21 1.80, 2.65 1.16, 1.70 1.19, 1.41 1.16, 1.58 1.07, 1.84 1.02, 1.67 1.03, 1.85 0.93, 1.32 1.15, 1.63 1.16, 1.68 0.79, 1.16 0.79, 1.55 0.55, 1.94 0.52, 1.51 0.94, 3.17 0.60, 1.72 0.57, 1.19 0.60, 1.38
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
0.82 0.81 0.75 0.82 0.90 0.87 0.79 0.75 0.89 0.86 0.91 0.91 0.76 0.96 0.88 0.87 0.85 0.97 0.93 0.97 1.01 0.70 0.87 0.86
0.76, 0.89 0.70, 0.94 0.59, 0.97 0.65, 1.04 0.66, 1.21 0.77, 0.99 0.65, 0.96 0.62, 0.89 0.82, 0.97 0.74, 1.00 0.69, 1.19 0.71, 1.17 0.58, 1.00 0.80, 1.15 0.74, 1.06 0.71, 1.05 0.70, 1.04 0.66, 1.40 0.50, 1.75 0.53, 1.77 0.49, 2.09 0.46, 1.07 0.60, 1.26 0.56, 1.32
0.89 0.82 0.90 0.78 0.76 0.96 0.91 0.81 0.93 0.84 0.87 0.86 0.79 1.03 0.98 0.93 0.79 0.89 0.74 0.94 1.02 0.66 0.76 0.84
0.82, 0.96 0.70, 0.95 0.70, 1.16 0.61, 0.99 0.55, 1.05 0.84, 1.10 0.74, 1.11 0.68, 0.98 0.85, 1.02 0.72, 0.98 0.66, 1.16 0.66, 1.11 0.60, 1.05 0.86, 1.23 0.81, 1.18 0.76, 1.13 0.65, 0.97 0.60, 1.30 0.39, 1.41 0.51, 1.73 0.48, 2.14 0.43, 1.03 0.52, 1.12 0.55, 1.30
Adjusted for age in years, sex, education, monthly expenditure, housing type, alcohol use, smoking, exercise, BMI, depression and objective health status.
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received or disease occurrence over the years of follow-up, which may mediate the association of SRH with mortality but not confound the association of SRH with mortality. Our question concerns the association of SRH with mortality rather than trajectories of health service use or the process by which poor SRH leads to mortality. Accessible high quality medical care is provided for all residents of Hong Kong (Department of Health, 2014), making it unlikely that poor SRH leads to mortality via differential health care utilization, although we cannot rule out the possibility that lack of health literacy may mediate the process by which SRH leads to mortality, and as such could be a potential target of intervention along with many social determinants of health. However, we did not find that the association of SRH with mortality varied with socioeconomic position, which might be an indicator of differential access to care or differential self-management. On the contrary the equitable access to care in Hong Kong (Department of Health, 2014) may relate to the lack of variation in the association of SRH with mortality by socioeconomic position. Our findings for age-comparative SRH are generally consistent with those in people of the same age with similar follow-up in the West, where worse age-comparative SRH is associated with a higher risk of death from all-causes, cardiovascular disease and respiratory disease, but not associated with death from cancer (Appels et al., 1996; Fernández-Ruiz et al., 2013; Sargent-Cox et al., 2010; Vuorisalmi et al., 2005). However, the magnitude of the association of age-comparative SRH with death from all- and specific causes in our setting is smaller than that in Western settings. Our findings of no difference in association of SRH with death by socioeconomic position are not inconsistent with studies from the West. People with more education might have a better appreciation of their health status. Accordingly, several studies from the West have found a stronger association for people with more education (Dowd and Zajacova, 2007; Huisman et al., 2007). However, humans are not particularly rational actors, and other studies have found stronger associations in people with less education (Singh-Manoux et al., 2007) or no variation by education (Van Doorslaer and Gerdtham, 2003). Studies concerning the association of SRH with death by income or occupation are similarly mixed (Burström and Fredlund, 2001; Singh-Manoux et al., 2007; Van Doorslaer and Gerdtham, 2003). Correspondingly, why some studies have found a stronger association in more advantaged socioeconomic groups is unclear as the characteristics of participants and follow-up duration were not substantially different. Nevertheless, age-comparative SRH may be a valid predictor of death across different socioeconomic groups in our non-Western setting. There are several explanations for the small magnitude of the association of SRH with mortality. First, in the West, the leading cause of death is cardiovascular disease (Lozano et al., 2013) but it is cancer in Hong Kong (Department of Health, 2012). SRH is less strongly associated with death from cancer than from cardiovascular disease (FernándezRuiz et al., 2013), thus more deaths from cancer may lead to a weaker association. Second, Hong Kong has long life expectancy (United Nations, 2013), so at any given age, Hong Kong people have longer to live than Westerners, when SRH is a better predictor of death in the short- than long-term. Third, people in the West may be more likely to report better age-comparative SRH (Sargent-Cox et al., 2010; Vuorisalmi et al., 2005) while people in our setting may be more “cautious” because moderation is favored in Chinese culture, which warns one to be vigilant when beyond others (Chen and Ma, 2002). Thus Chinese people may report “normal” SRH even when they are in good health. On the other hand, older people may be more superstitious, particularly in China, so they might be less willing to report poor health for fear of bringing bad luck and bad health (Li, 2011). Moreover, our participants were less likely to be current smokers or moderate drinkers than older people from the West (Fernández-Ruiz et al., 2013). As such, SRH may have less discrimination in Chinese people thereby weakening the association of age-comparative SRH with death. Fourth, older Chinese may be more likely to report non-fatal illness than people
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in the West (Sadana et al., 2000), which may also result in the smaller magnitude of association. Our study found that the association of age-comparative SRH with death from stroke varied by sex, with the association stronger for men than women. Given that stroke usually occurs at younger ages for men than women (Appelros et al., 2009), age-adjusted baseline agecomparative SRH may be a better predictor for men. The much weaker association of age-comparative SRH with death from all-causes in participants aged ≥85 years could be due to inaccurate estimation of health status because of cognitive problems. In contrast, worse self-comparative SRH was not associated with higher risk of death, consistent with previous studies (Bath, 2003; Deeg and Kriegsman, 2003; Fernández-Ruiz et al., 2013; Sargent-Cox et al., 2010). The association did not vary by age-comparative SRH. The distribution of self-comparative SRH differed from that of age-comparative SRH with most participants reporting normal or worse self-comparative SRH. Better age-comparative SRH may be an indication of good health, but better self-comparative SRH may reflect temporary amelioration of chronic diseases and symptoms. Self-comparative SRH has a U-shaped relation with several health indices (Li et al., 2006), which may underlie the lower risks of death from all- and specific causes for those with normal self-comparative SRH. Besides, older people may lower their standard for a healthy state and those with objectively “poor health” often rate their health as good (King, 2002). Conclusion In Hong Kong, the most westernized city of China, age-comparative SRH predicted death among older people although the magnitude of association was smaller than that in Western populations, possibly because of a different cause-composition of mortality, long life expectancy or contextually specific assessments of health. Consistent with Western studies, age-comparative SRH also predicted death from cardiovascular and respiratory diseases more strongly than death from cancer. The association of age-comparative SRH with death did not vary by socioeconomic position. In contrast, worse self-comparative SRH did not predict higher mortality. Conflict of interest The authors declares that there is no competing interests. Acknowledgments We wish to thank the staff of the Elderly Health Centers and the Hospital Authority for their assistance in data collection and entry. References Alfonso, H., Beer, C., Yeap, B.B., Hankey, G.J., Flicker, L., Almeida, O.P., 2012. Perception of worsening health predicts mortality in older men: the Health in Men Study (HIMS). Arch. Gerontol. Geriatr. 55, 363–368. Altman, D.G., Bland, J.M., 2003. Interaction revisited: the difference between two estimates. BMJ 326, 219. Appelros, P., Stegmayr, B., Terént, A., 2009. Sex differences in stroke epidemiology: a systematic review. Stroke 40, 1082–1090. Appels, A., Bosma, H., Grabauskas, V., Gostautas, A., Sturmans, F., 1996. Self-rated health and mortality in a Lithuanian and a Dutch population. Soc. Sci. Med. 42, 681–689. Bath, P.A., 2003. Differences between older men and women in the self-rated health— mortality relationship. The Gerontologist 43, 387–395. Burström, B., Fredlund, P., 2001. Self rated health: is it as good a predictor of subsequent mortality among adults in lower as well as in higher social classes? J. Epidemiol. Community Health 55, 836–840. Chen, G., Ma, R., 2002. The impact of harmony on Chinese conflict management. Chin. Confl. Manag. Resolut. 3–17. Cotter, K.A., Lachman, M.E., 2010. Psychosocial and behavioural contributors to health: age-related increases in physical disability are reduced by physical fitness. Psychol. Health 25, 805–820. de Bruin, A., Picavet, H.S., Nossikov, A., 1996. Health interview surveys: towards international harmonization of methods and instruments. WHO Reg. Publ. Eur. Ser. 58, i-xiii, pp. 1–161.
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Deeg, D.J., Kriegsman, D.M., 2003. Concepts of self-rated health: specifying the gender difference in mortality risk. The Gerontologist 43, 376–386. Department of Health HK, 2012. Age-standardised death rates by leading causes of death, 2001–2012. http://www.chp.gov.hk/en/data/4/10/27/339.html. Department of Health HK, 2014. Overview of the health care system in Hong Kong. http:// www.gov.hk/en/residents/health/hosp/overview.htm. Dowd, J.B., Zajacova, A., 2007. Does the predictive power of self-rated health for subsequent mortality risk vary by socioeconomic status in the US? Int. J. Epidemiol. 36, 1214–1221. Eriksson, I., Undén, A.-L., Elofsson, S., 2001. Self-rated health. Comparisons between three different measures. Results from a population study. Int. J. Epidemiol. 30, 326–333. Fernández-Ruiz, M., Guerra-Vales, J.M., Trincado, R., et al., 2013. The ability of self-rated health to predict mortality among community-dwelling elderly individuals differs according to the specific cause of death: data from the NEDICES cohort. Gerontology 59, 368–377. Heistaro, S., Jousilahti, P., Lahelma, E., Vartiainen, E., Puska, P., 2001. Self rated health and mortality: a long term prospective study in eastern Finland. J. Epidemiol. Community Health 55, 227–232. Ho, S.C., 1991. Health and social predictors of mortality in an elderly Chinese cohort. Am. J. Epidemiol. 133, 907–921. Huisman, M., van Lenthe, F., Mackenbach, J., 2007. The predictive ability of self-assessed health for mortality in different educational groups. Int. J. Epidemiol. 36, 1207–1213. Idler, E.L., Benyamini, Y., 1997. Self-rated health and mortality: a review of twenty-seven community studies. J. Health Soc. Behav. 38, 21–37. Johnson, R.K., 1998. Language and Education in Hong Kong. Language in Hong Kong at Century's End. pp. 265–281. King, M., 2002. Adaptation to changing health: response shift in quality of life research. Qual. Life Res. 11, 185–187. Leung, K., 2010. Beliefs in Chinese culture. The Oxford Handbook of Chinese Psychology, pp. 221–240. Leung, K.K., Tang, L.Y., Lue, B.H., 1997. Self-rated health and mortality in Chinese institutional elderly persons. J. Clin. Epidemiol. 50, 1107–1116. Li, X., 2011. Reasons for the aged to be superstitious. China J. Health Psychol. 9, 1148–1152. Li, Z.B., Ho, S.Y., Chan, W.M., et al., 2004. Obesity and depressive symptoms in Chinese elderly. Int. J. Geriatr. Psychiatry 19, 68–74. Li, Z.B., Lam, T.H., Ho, S.Y., et al., 2006. Age‐versus time‐comparative self-rated health in Hong Kong Chinese older adults. Int. J. Geriatr. Psychiatry 21, 729–739. Lima-Costa, M.F., Cesar, C.C., Chor, D., Proietti, F.A., 2012. Self-rated health compared with objectively measured health status as a tool for mortality risk screening in older adults: 10-year follow-up of the Bambui Cohort Study of Aging. Am. J. Epidemiol. 175, 228–235. Lozano, R., Naghavi, M., Foreman, K., et al., 2013. Global and regional mortality from 235 causes of death for 20 age groups in 1990 and 2010: a systematic analysis for the Global Burden of Disease Study 2010. Lancet 380, 2095–2128.
Maddison, A., 2007. The World Economy Volume 1: A Millennial Perspective Volume 2: Historical Statistics. Development Centre of the Organisation for Economic Cooperation and Development. Møller, L., Kristensen, T.S., Hollnagel, H., 1996. Self rated health as a predictor of coronary heart disease in Copenhagen, Denmark. J. Epidemiol. Community Health 50, 423–428. Montlahuc, C., Soumare, A., Dufouil, C., et al., 2011. Self-rated health and risk of incident dementia: a community-based elderly cohort, the 3C study. Neurology 77, 1457–1464. Moore, C.A., 1967. The Chinese Mind: Essentials of Chinese Philosophy and Culture. University of Hawaii Press. Mossey, J.M., Shapiro, E., 1982. Self-rated health: a predictor of mortality among the elderly. Am. J. Public Health 72, 800–808. Sadana, R.,Mathers, C.D., Lopez, A.D., Murray, C.J., Iburg, K., 2000. Comparative Analyses of More Than 50 Household Surveys on Health Status. World Health Organization, Geneva. Sargent-Cox, K.A.,Anstey, K.J.,Luszcz, M.A., 2010. The choice of self-rated health measures matter when predicting mortality: evidence from 10 years follow-up of the Australian longitudinal study of ageing. BMC Geriatr. 10, 18. Schooling, C.M.,Lam, T.H.,Li, Z.B., et al., 2006. Obesity, physical activity, and mortality in a prospective Chinese elderly cohort. Arch. Intern. Med. 166, 1498–1504. Singh-Manoux, A., Guéguen, A., Martikainen, P., Ferrie, J., Marmot, M., Shipley, M., 2007. Self-rated health and mortality: short-and long-term associations in the Whitehall II study. Psychosom. Med. 69, 138–143. Sun, W.J., Xu, L., Chan, W.M., Lam, T.H., Schooling, C.M., 2013. Are depressive symptoms associated with cardiovascular mortality among older Chinese: a cohort study of 64,000 people in Hong Kong? Am. J. Geriatr. Psychiatry 21, 1107–1115. United Nations, 2013. Department of Economic and Social Affairs, World Population Prospects: The 2012 Revision. Van Doorslaer, E., Gerdtham, U.-G., 2003. Does inequality in self-assessed health predict inequality in survival by income? Evidence from Swedish data. Soc. Sci. Med. 57, 1621–1629. Vuorisalmi, M.,Lintonen, T.,Jylhä, M., 2005. Global self-rated health data from a longitudinal study predicted mortality better than comparative self-rated health in old age. J. Clin. Epidemiol. 58, 680–687. Wilcox, V.L., Kasl, S.V., Idler, E.L., 1996. Self-rated health and physical disability in elderly survivors of a major medical event. J. Gerontol. Ser. B Psychol. Sci. Soc. Sci. 51, S96–S104. Xu, L., Schooling, C.M., Chan, W.M., Lee, S.Y., Leung, G.M., Lam, T.H., 2013. Smoking and hemorrhagic stroke mortality in a prospective cohort study of older Chinese. Stroke 44, 2144–2149. Young, H.,Grundy, E.,O'Reilly, D.,Boyle, P., 2010. Self-rated health and mortality in the UK: results from the first comparative analysis of the England and Wales, Scotland, and Northern Ireland longitudinal studies. Popul. Trends 139, 11–36.
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Preventive Medicine journal homepage: www.elsevier.com/locate/ypmed
Self-rated health and mortality in a prospective Chinese elderly cohort study in Hong Kong Chen Shen a, C. Mary Schooling a,c,⁎, Wai Man Chan b, Jiang Xiu Zhou a, Janice M. Johnston a, Siu Yin Lee b, Tai Hing Lam a a b c
School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China Department of Health, Hong Kong SAR, China School of Public Health, The City University of New York and Hunter College, NY, USA
a r t i c l e
i n f o
Available online 18 July 2014 Keywords: Aging Cohort study Mortality Self-rated health
a b s t r a c t Objectives. In the West, self-rated health reliably predicts death, but conceptualizations of health and causecomposition of mortality may be contextually specific. Little is known as to how self-rated health predicts death in non-Western settings. Methods. Multivariable Cox regression analysis was used to assess the adjusted associations of age-comparative and self-comparative self-rated health with death from all- and specific-causes using a population-based cohort of 66,820 Chinese (65+ years) enrolled from 1998 to 2001 at 18 Elderly Health Centers in Hong Kong, and followed until May 31, 2012. Results. During an average of 10.9 years follow-up, 19,845 deaths occurred with 6336 from cancer. Worse age-comparative self-rated health, compared with better, was positively associated with death from all-causes (hazard ratio 1.68, 95% confidence interval 1.59, 1.77), cardiovascular disease (hazard ratio 1.83, 95% confidence interval 1.66, 2.02), stroke (hazard ratio 1.93, 95% confidence interval 1.63, 2.29), ischemic heart disease (hazard ratio 1.77, 95% confidence interval 1.51, 2.08), cancer (hazard ratio 1.17, 95% confidence interval 1.06, 1.30) and respiratory disease (hazard ratio 2.25, 95% confidence interval 2.01, 2.52), adjusted for age and sex. Selfcomparative self-rated health was not associated with higher mortality. Conclusion. Age-comparative self-rated health predicted death in older people from a non-Western setting although the association was less marked than in Western settings. © 2014 Elsevier Inc. All rights reserved.
Introduction Self-rated health (SRH), a subjective assessment of health status, is a powerful predictor of mortality in older persons. SRH is as an important health indicator which is easy to measure and provides a good reflection of health status (de Bruin et al., 1996). SRH may be assessed as global SRH using questions such as “What do you think of your health in general?” (Eriksson et al., 2001; Idler and Benyamini, 1997) or as comparative SRH, including age-comparative SRH (comparing oneself to other people of the same age) and self-comparative SRH (comparing oneself to one's own status a year earlier) (Alfonso et al., 2012; Fernández-Ruiz et al., 2013). In the West, measurement methods for SRH such as type of scale, wording of the question and number of
Abbreviations: BMI, body mass index; CI, confidence interval; EHC, elderly health center; GDS, Geriatric Depression Scale; HR, hazard ratio; ICD, International Classification of Disease; IHD, ischemic heart disease; RRR, relative risk ratio; SRH, self-rated health. ⁎ Corresponding author at: School of Public Health at Hunter College, The City University of New York, 2180 Third Avenue, New York, NY 10035, USA. E-mail address: [email protected] (C.M. Schooling).
http://dx.doi.org/10.1016/j.ypmed.2014.07.018 0091-7435/© 2014 Elsevier Inc. All rights reserved.
options differ; both global and age-comparative SRH predict death (Fernández-Ruiz et al., 2013; Lima-Costa et al., 2012; Young et al., 2010) although comparisons are not always consistent. Sargent-Cox et al. (2010) reported that global SRH was a better predictor of allcause mortality than age-comparative SRH while Fernández-Ruiz et al. (2013) reported that age-comparative SRH was better. However, selfcomparative SRH is a weaker predictor of mortality (Bath, 2003; Fernández-Ruiz et al., 2013). The magnitude of association of SRH with mortality may vary by cause of death. SRH might be more strongly associated with diseases with a prolonged course and substantial impact on daily life, such as cardiovascular and respiratory diseases, than diseases without notable signs in the early stages which then develop rapidly such as cancer (Fernández-Ruiz et al., 2013). SRH is easy to measure, and could be a health indicator for older people given it might reveal health status before symptoms develop. Most studies of the association of SRH with mortality relate to Western populations, where associations may vary by socioeconomic position (Burström and Fredlund, 2001; Huisman et al., 2007; Møller et al., 1996; Mossey and Shapiro, 1982). However, these observations may not generalize to other settings because of contextually-specific
C. Shen et al. / Preventive Medicine 67 (2014) 112–118
cause-composition of mortality, culturally-specific perceptions of health and varying social patterning of health-related attributes. In the West, cardiovascular disease is the leading cause of death, but cancer is the leading cause of death in Hong Kong (Lozano et al., 2013). Moreover, self-ratings tend to be optimistic in the West (Heistaro et al., 2001; Montlahuc et al., 2011) but other cultures may favor moderation, such as the Chinese “doctrine of the mean” (Leung, 2010; Li et al., 2004; Moore, 1967) which may make people rate their health as “normal”. Finally, socioeconomic patterning may be less entrenched in settings where economic development is recent (Maddison, 2007) and socioeconomic disadvantage has not been perpetuated over generations. Few studies have addressed the association of SRH with mortality in non-Western settings, often with short follow-up and small samples (Ho, 1991; Leung et al., 1997). We have previously reported that agecomparative SRH was more strongly associated with concurrent physical conditions than self-comparative SRH (Li et al., 2006) as well as that depression was associated with SRH and mortality (Sun et al., 2013). Here, we examined the role of SRH in predicting death from all- and specific causes in a developed non-Western setting, where cardiovascular disease is not the leading cause of death (Lozano et al., 2013), cultural preferences emphasize moderation (Leung, 2010; Moore, 1967) and universal education is recent (Johnson, 1998). We also examined whether any associations varied by socioeconomic position. Methods Source of data Since July 1998, eighteen Elderly Health Centers (EHC) have been established by the Hong Kong Government Department of Health to offer older people screening services and medical examinations, aiming to enhance primary health care by improving self-care ability, encouraging healthy living and strengthening social integration. All residents of Hong Kong aged ≥65 years were encouraged to enroll for a small annual fee of HK$110 (US$1 = HK$7.8; waived for those on public social security assistance). This cohort study covered all 66,820 enrollees from July 1998 to December 2001. More women were enrolled than men (44,140 versus 22,680); otherwise, age, socioeconomic position, current smoking status and hospital use were similar to the general older population (Schooling et al., 2006; Xu et al., 2013). Nurses and doctors conducted health assessments, using standardized structured interviews, and comprehensive clinical examinations. Information on demographic characteristics, socioeconomic position, lifestyle, and disease history was collected, as described elsewhere (Schooling et al., 2006; Xu et al., 2013). Ethics approval was obtained from The University of Hong Kong–Hospital Authority Hong Kong West Cluster Joint Institutional Review Board. Measures
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of health services (2 items: regular use of medication and any hospital admission in the last year), frailty (3 items: cognitive impairment, functional impairment and two or more falls in the last 6 months), and unintentional weight loss of more than 4.5 kg in the last 6 months (Schooling et al., 2006). The Kunder–Richardson-20 coefficient which was used to determine the internal consistency of the index with dichotomous responses was 0.44. Follow-up Vital status was ascertained by record linkage to death registration in Hong Kong on unique Hong Kong identity card number. The last date of follow-up or censor date for living participants was May 31, 2012. Most participants in the EHC cohort remain in Hong Kong, any deaths outside Hong Kong are also usually registered in Hong Kong. Where vital status could not be ascertained from death registration or record linkage to use of routine services, regular telephone interviews were conducted in 2004, 2006 and 2009 to obtain vital status and cause of death. Causes of death were routinely coded by International Classification of Diseases (ICD) 9th Reversion before 2001 and 10th Reversion after 2001 and checked by the Department of Health. Most Hong Kong residents died in hospital, ensuring accurate ascertainment of cause of death, which we have used in previous studies (Schooling et al., 2006; Xu et al., 2013). Those whose vital status could not be determined were assumed to be alive. The outcomes were death from all-causes, cardiovascular disease (ICD9 401–459 or ICD10 I10–I99), ischemic heart disease (IHD) (ICD9 410–414 or ICD10 I20–I25), stroke (ICD9 430–438 or ICD10 I60–I69), cancer (ICD9 140–239 or ICD10 C00–C97, D00–D48) and respiratory disease (ICD9 460–519 or ICD10 J00–J99). Statistical analysis Chi-square tests were used to compare baseline characteristics by age- and self-comparative SRH. Multivariable Cox regression was used to estimate adjusted hazard ratios (HR) with 95% confidence intervals (CI) for death from all- and specific causes. The proportional hazards assumption was checked by visual inspection of plots of log (− log S) against time, where S is the estimated survival function. Models were built in stages. Model 1 adjusted for age and sex. Model 2 additionally adjusted for socioeconomic position (education, monthly expenditure and housing type), lifestyle (alcohol use, smoking and exercise), body mass index (BMI) and depression as Geriatric Depression Scale (GDS) score ≥ 8. Model 3 additionally adjusted for objective health status. Whether associations varied by sex, age or socioeconomic position was assessed from the significance of interaction terms and the heterogeneity of estimates across strata. We repeated the analysis by follow-up duration including short-term (b 5 years) and long-term (excluding all deaths within first 5 years). We used the relative risk ratio (RRR) to assess differences in these associations (Altman and Bland, 2003).
SRH was assessed at baseline from two verbal questions: (1) How would you rate your health condition compared with others of your age? (age-comparative SRH) (2) How would you rate your health condition this year compared with last year? (self-comparative SRH) Both questions had three response options: better, normal and worse. Objective health status Several morbidity, comorbidity, or prognostic indices for older people exist, but not for Asians in a primary care setting. We used our previously constructed, simple but comprehensive 11-item index by counting chronic conditions (5 items: heart disease, stroke, diabetes, chronic obstructive pulmonary disease and/or asthma, and hypertension), use
Results Among 66,820 participants (22,680 men and 44,140 women) enrolled at baseline from 1998 to 2001, 66,814 (99.9%) with age- and self-comparative SRH were included here. Of 66,820 participants, 62,824 had vital status ascertained from record linkage including 19,452 deaths, 2539 had vital status obtained by telephone interview including 393 deaths, and 1457 had unknown vital status and were presumed to be alive. The mean follow-up was 10.9 years (standard deviation = 3.1). Of the 19,845 deaths, 6336 were from cancer (31.9%), 5651 from cardiovascular disease and 4060 from respiratory disease. Most people had better or normal age-comparative SRH (92.3%) but normal or worse self-comparative SRH (93.6%). Table 1 shows baseline characteristics by age- and self-comparative SRH for men and women. Women were more likely to report worse age- and self-comparative
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Table 1 Baseline characteristics by age- and self-comparative SRH in 66,814 older people enrolled at EHCs in Hong Kong from 1998 to 2001. Age-comparative SRH
Self-comparative SRH
Men (n = 22,678)
Age group (%)
Education (%)
Housing type (%)
Alcohol (%)
Smoking (%)
Exercise (%)
BMI (%)
GDS score (%) Health status (%)
Men (n = 22,678)
Women (n = 44,136)
Better (n = 6739)
Normal (n = 14740)
Worse (n = 1199)
Better (n = 9125)
Normal (n = 31067)
Worse (n = 3944)
Better (n = 1464)
Normal (n = 14039)
Worse (n = 7175)
Better (n = 2821)
Normal (n = 25329)
Worse (n = 15986)
67.5 29.4 3.1 36.3 49.8 8.6 5.3 22.9 27.5 37.5 12.1 55.8 38.5 5.7 46.9 16.9 25.2 11.0 38.4 20.1 41.6 14.8 25.3 59.9 4.7 33.3 24.3 37.7 94.9 5.1 17.0 29.1 21.5 19.0 13.4
70.9 26.3 2.8 28.7 51.9 11.5 8.0 19.5 34.3 35.2 11.1 55.4 39.3 5.3 49.6 18.0 23.2 9.2 38.3 20.5 41.2 17.1 24.1 58.8 5.7 33.5 24.5 36.3 93.5 6.5 15.3 24.8 21.9 21.6 16.4
68.2 28.7 3.1 25.3 52.2 11.4 11.1 18.2 29.6 36.5 15.7 46.3 45.8 7.9 49.9 26.0 16.3 7.9 31.6 22.9 45.6 22.7 27.3 50.0 14.0 34.6 20.1 31.3 74.5 25.5 5.4 14.6 20.0 22.4 37.7
67.1 28.3 4.7 13.8 31.1 19.4 35.7 16.5 27.3 39.5 16.6 53.4 38.9 7.7 82.1 5.7 11.0 1.2 87.1 4.2 8.7 13.1 28.3 58.6 4.2 31.5 22.2 42.1 93.7 6.3 15.8 29.6 21.1 19.2 14.2
69.3 27.0 3.7 9.4 29.1 20.7 40.8 13.5 31.0 39.5 16.0 53.0 39.6 7.3 85.1 5.3 8.7 1.0 88.8 3.9 7.3 14.8 27.6 57.7 5.0 30.7 21.9 42.4 90.2 9.8 13.5 24.8 21.7 21.6 18.4
67.4 28.4 4.2 7.7 25.9 19.7 46.8 16.1 26.2 37.8 19.9 48.9 44.9 6.2 84.4 8.1 6.7 0.8 86.7 4.0 9.4 17.8 30.2 52.0 7.4 31.5 19.4 41.6 69.4 30.6 7.2 16.8 19.7 23.3 33.0
70.1 27.1 2.8 32.0 49.3 11.3 7.4 20.7 31.5 35.4 12.4 54.4 37.8 7.8 48.9 22.8 19.3 9.0 34.5 17.7 47.8 12.8 22.5 64.7 6.4 33.0 26.3 34.3 95.1 4.9 11.3 24.6 21.1 22.2 20.9
71.8 25.7 2.5 31.4 51.5 10.3 6.8 20.5 32.8 35.5 11.2 55.9 38.7 5.4 49.9 16.1 24.1 10.0 41.0 19.1 39.9 16.0 23.9 60.1 4.9 32.6 25.0 37.4 95.8 4.2 17.3 27.2 21.7 20.3 13.5
65.8 30.5 3.7 29.3 51.3 11.1 8.3 20.5 30.5 36.9 12.2 53.5 41.1 5.4 46.7 21.0 23.1 9.2 32.8 23.7 43.5 18.8 26.5 54.7 7.6 35.4 22.1 35.0 86.9 13.1 12.2 22.4 21.9 21.6 22.0
70.4 26.2 3.4 10.6 27.1 20.5 41.8 17.1 28.5 38.1 16.3 50.4 40.4 9.2 82.7 7.6 8.9 0.9 86.5 3.8 9.6 11.2 29.0 59.8 5.2 30.5 21.3 43.1 91.2 8.8 10.2 25.4 21.3 21.7 21.3
70.6 25.6 3.8 10.4 29.9 20.3 39.4 13.6 31.1 39.7 15.7 53.6 38.8 7.6 85.2 4.7 9.0 1.1 89.5 3.7 6.9 14.2 27.2 58.6 4.7 31.0 22.1 42.2 93.4 6.6 15.2 26.9 21.4 20.9 15.6
65.4 30.4 4.2 9.7 28.6 20.3 41.5 15.1 28.0 39.1 17.8 51.8 41.8 6.5 83.6 6.7 8.9 0.9 86.7 4.5 8.7 16.0 29.0 55.0 5.7 31.0 21.1 42.2 81.8 18.2 11.2 22.1 21.5 21.8 23.4
Two-sided p value from a χ2 test between SRH and baseline characteristics: all b0.05.
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Monthly expenditure (%)
65–74 75–84 ≥85 Secondary above Primary No formal but literate Illiterate ≥3000HK$ 2000–2999HK$ 1000–1999HK$ b1000HK$ Private Public or aided Temporary or others Never drinker Ex-drinker Social drinker Regular drinker Never smoker Current smoker Ex-smoker Never b30 min/day ≥30 min/day b18.5 18.5– b 23 23– b 25 ≥25 b8 ≥8 0 1 2 3 4 or more
Women (n = 44,136)
C. Shen et al. / Preventive Medicine 67 (2014) 112–118
SRH than men (p values b 0.01). Compared with better age- and selfcomparative SRH, participants with worse age- and self-comparative SRH had lower socioeconomic position, and were more likely to be ever smokers, physically inactive, underweight and to have depression (all p values b 0.05). Age-comparative SRH had a graded association with objective health status but self-comparative SRH had a U-shaped association with objective health status. Participants with normal selfcomparative SRH had the best objective health status. Table 2 shows that compared with better age-comparative SRH, both normal and worse age-comparative SRH were associated with a higher risk of death from all-causes, cardiovascular disease and respiratory disease, but only weakly associated with death from cancer, adjusted for age, sex, socioeconomic position, lifestyle, BMI, depression and objective health status. The association of age-comparative SRH with death from all-causes attenuated substantially after adjusting for objective health status. Discrimination ability from the C statistic was 0.704 (95% CI 0.701, 0.708) for model 2 and 0.722 (95% CI 0.718, 0.726) for model 3. Relative to better self-comparative SRH, normal selfcomparative SRH was associated with a lower risk of death from allcauses, cardiovascular disease, respiratory disease and cancer after similar adjustment. Worse self-comparative SRH was also associated with a lower risk of death from all-cause and cardiovascular disease, but not associated with death from cancer or respiratory disease. The association of self-comparative SRH with death from all- and specific causes did not vary with age-comparative SRH (all p values N 0.05). The association of age-comparative SRH with death from cardiovascular disease and stroke varied by sex (p values for interaction 0.04 and 0.004, respectively). Table 3 shows sex-specific analysis of ageand self-comparative SRH with death from all- and specific causes.
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Men with worse age-comparative SRH had a higher relative ratio of death from cardiovascular disease (RRR = 1.27, 95% CI 1.02, 1.57) and stroke (RRR = 1.76, 95% CI 1.22, 2.54) than women. The association of age- and self-comparative SRH with all-cause mortality varied by age (p values for interaction 0.03 and 0.03, respectively). The association of worse age-comparative SRH with all-cause mortality was weaker in the participants aged ≥ 85, as shown in Table 4. The associations of worse self-comparative SRH with death from all- and specific-causes were similar across different age groups, but the associations of normal self-comparative SRH with all- and specific-causes were stronger among younger age groups. The associations of SRH with death from all- and specific-causes did not vary by socioeconomic position or objective health status (all p values N 0.05). The pattern of associations of SRH with death was similar when stratified by follow-up duration. The magnitude of association of worse age-comparative SRH with all-cause mortality was stronger in the short-term than the long-term (RRR = 1.13, 95% CI 1.01, 1.28), adjusted for age, sex, socioeconomic position, lifestyle, BMI, depression and objective health status. The magnitude of association of worse selfcomparative SRH with all-cause mortality was similar in the short- and long-term (RRR = 0.97, 95% CI 0.86, 1.09). Discussion In this understudied non-Western population, age-comparative SRH predicted death in older people after adjusting for age, sex, socioeconomic position, lifestyle, BMI, depression and objective health status, indicating that age-comparative SRH may act as a proxy of unmeasured signs or symptoms of diseases as age-comparative SRH was also
Table 2 Adjusted associations of age- and self-comparative SRH with death from all- and specific causes in 66,814 older people enrolled at EHCs in Hong Kong from 1998 to 2001 and followed up until May 31, 2012. Age-comparative SRH
All-causes Model 1 Model 2 Model 3 All cardiovascular disease Model 1 Model 2 Model 3 Stroke Model 1 Model 2 Model 3 IHD Model 1 Model 2 Model 3 Other cardiovascular disease Model 1 Model 2 Model 3 All cancer Model 1 Model 2 Model 3 All respiratory disease Model 1 Model 2 Model 3 Other diseases Model 1 Model 2 Model 3
Self-comparative SRH
Better
Normal
Worse
Better
HR
HR
95% CI
HR
Normal
95% CI
HR
HR
95% CI
HR
1 1 1
1.14 1.10 1.06
1.10, 1.18 1.06, 1.14 1.02, 1.09
1 1 1
1.21 1.17 1.11
1 1 1
95% CI
1.68 1.45 1.24
1.59, 1.77 1.37, 1.53 1.17, 1.31
1 1 1
0.78 0.81 0.86
0.74, 0.83 0.77, 0.86 0.81, 0.91
0.94 0.92 0.91
0.89, 1.01 0.87, 0.97 0.86, 0.96
1.13, 1.29 1.10, 1.25 1.04, 1.18
1.83 1.63 1.28
1.66, 2.02 1.47, 1.80 1.15, 1.42
1 1 1
0.75 0.78 0.85
0.68, 0.83 0.70, 0.86 0.77, 0.94
0.87 0.86 0.84
0.79, 0.97 0.77, 0.96 0.76, 0.94
1.26 1.22 1.15
1.13, 1.42 1.09, 1.36 1.03, 1.29
1.93 1.68 1.34
1.63, 2.29 1.41, 2.00 1.13, 1.61
1 1 1
0.75 0.77 0.83
0.63, 0.89 0.65, 0.92 0.70, 0.99
0.92 0.89 0.88
0.77, 1.11 0.75, 1.07 0.73, 1.05
1 1 1
1.15 1.12 1.04
1.04, 1.27 1.01, 1.24 0.94, 1.16
1.77 1.58 1.21
1.51, 2.08 1.34, 1.87 1.02, 1.42
1 1 1
0.76 0.79 0.88
0.65, 0.90 0.67, 0.94 0.74, 1.03
0.87 0.85 0.84
0.73, 1.02 0.72, 1.01 0.71, 0.99
1 1 1
1.24 1.21 1.14
1.09, 1.41 1.06, 1.37 1.00, 1.29
1.79 1.64 1.30
1.48, 2.18 1.34, 2.00 1.07, 1.59
1 1 1
0.74 0.77 0.84
0.61, 0.90 0.64, 0.94 0.69, 1.02
0.83 0.83 0.81
0.68, 1.01 0.68, 1.01 0.66, 0.99
1 1 1
0.99 0.97 0.97
0.93, 1.05 0.92, 1.03 0.91, 1.02
1.17 1.09 1.05
1.06, 1.30 0.98, 1.21 0.95, 1.17
1 1 1
0.87 0.89 0.90
0.79, 0.96 0.80, 0.98 0.81, 0.99
1.00 0.97 0.97
0.90, 1.11 0.88, 1.08 0.87, 1.08
1 1 1
1.27 1.20 1.14
1.17, 1.37 1.11, 1.29 1.06, 1.23
2.25 1.71 1.45
2.01, 2.52 1.52, 1.93 1.28, 1.63
1 1 1
0.75 0.79 0.85
0.66, 0.85 0.70, 0.90 0.75, 0.96
0.98 0.95 0.93
0.87, 1.11 0.83, 1.07 0.82, 1.06
1 1 1
1.20 1.14 1.08
1.11, 1.30 1.05, 1.23 1.00, 1.17
1.89 1.58 1.29
1.68, 2.13 1.39, 1.79 1.14, 1.46
1 1 1
0.72 0.75 0.81
0.64, 0.82 0.66, 0.85 0.71, 0.92
0.91 0.89 0.87
0.80, 1.03 0.78, 1.01 0.77, 0.99
Model 1: adjusted for age group and sex. Model 2: adjusted for age group, sex, education, monthly expenditure, housing type, alcohol use, smoking, exercise, BMI and depression. Model 3: additionally adjusted for objective health status.
Worse
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Table 3 Sex-specific adjusteda associations of age- and self-comparative SRH with death from all- and specific causes in 66,814 older people enrolled at EHCs in Hong Kong from 1998 to 2001 and followed up until May 31, 2012. Age-comparative SRH
Sex Men
Women
a
All-causes All cardiovascular disease Stroke IHD Other cardiovascular disease All cancer All respiratory disease Other diseases All-causes All cardiovascular disease Stroke IHD Other cardiovascular disease All cancer All respiratory disease Other diseases
Self-comparative SRH
Better
Normal
Worse
Better
Normal
Worse
HR
HR
95% CI
HR
95% CI
HR
HR
95% CI
HR
95% CI
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1.03 1.10 1.16 1.01 1.18 0.93 1.11 1.07 1.08 1.11 1.15 1.07 1.10 1.00 1.18 1.10
0.99, 1.09 1.00, 1.21 0.98, 1.38 0.87, 1.18 0.97, 1.44 0.86, 1.01 1.00, 1.23 0.95, 1.20 1.03, 1.13 1.01, 1.21 0.98, 1.33 0.93, 1.24 0.93, 1.30 0.92, 1.09 1.05, 1.33 0.98, 1.22
1.22 1.52 1.97 1.30 1.35 0.94 1.46 1.03 1.26 1.20 1.12 1.19 1.28 1.13 1.46 1.42
1.12, 1.34 1.28, 1.81 1.48, 2.62 0.98, 1.71 0.92, 1.97 0.79, 1.13 1.23, 1.73 0.82, 1.30 1.17, 1.35 1.05, 1.36 0.89, 1.41 0.97, 1.47 1.01, 1.64 0.99, 1.29 1.23, 1.73 1.21, 1.65
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
0.84 0.78 0.69 0.83 0.81 0.82 0.93 0.86 0.87 0.90 0.94 0.90 0.85 0.98 0.79 0.78
0.77, 0.91 0.66, 0.91 0.53, 0.91 0.65, 1.07 0.58, 1.12 0.71, 0.94 0.78, 1.11 0.70, 1.06 0.81, 0.94 0.79, 1.02 0.74, 1.18 0.73, 1.12 0.66, 1.08 0.85, 1.12 0.66, 0.94 0.67, 0.92
0.93 0.83 0.83 0.83 0.82 0.88 1.07 0.99 0.90 0.86 0.91 0.85 0.81 1.06 0.83 0.81
0.85, 1.01 0.70, 0.98 0.63, 1.11 0.64, 1.08 0.58, 1.15 0.75, 1.02 0.89, 1.29 0.80, 1.23 0.83, 0.97 0.75, 0.98 0.72, 1.16 0.68, 1.06 0.63, 1.04 0.92, 1.23 0.69, 0.99 0.69, 0.95
Adjusted for age group, education, monthly expenditure, housing type, alcohol use, smoking, exercise, BMI, depression and objective health status.
strongly related to objective health status. The association was stronger for death from cardiovascular disease and respiratory disease than for death from cancer. Men with worse age-comparative SRH had a higher relative ratio of death from cardiovascular disease and stroke than women. The association of worse age-comparative SRH with all-cause mortality was stronger in younger age groups and in the short-term. The associations of age-comparative SRH with death from all- and specific causes did not differ by socioeconomic position. In contrast, worse self-comparative SRH did not predict higher mortality, and the results did not differ by sex, socioeconomic position, follow-up duration, cause of death or age-comparative SRH. Despite using a large prospective cohort with long term follow-up, this study has limitations. First, SRH was assessed at baseline, but may change with age. However, SRH is stable over time, even after major
medical events (Cotter and Lachman, 2010; Wilcox et al., 1996). Second, global SRH is not available, so we cannot assess whether global or comparative SRH predicts death better. Third, participants might be healthier than the general older population because the EHC may attract older people who are ambulatory and more health conscious. However, the associations of age- and self-comparative SRH with death did not vary with health status. Fourth, objective health status was defined based on self-report with relatively low internal consistency perhaps because this index is an overall assessment of health status with independent items. However, this health status index has a clear graded association with death in this cohort (Schooling et al., 2006), suggesting its validity. Although we cannot rule out recall bias, the use of simple yes/no questions in assessing chronic conditions might minimize recall error. Fifth, we did not have information on the health care participants
Table 4 Age-specific adjusteda associations of age- and self-comparative SRH with death from all- and specific causes in 66,814 older people enrolled at EHCs in Hong Kong from 1998 to 2001 and followed up until May 31, 2012. Age-comparative SRH
Age group 65–74
75–84
≥85
a
All-causes All cardiovascular disease Stroke IHD Other cardiovascular disease All cancer All respiratory disease Other diseases All-causes All cardiovascular disease Stroke IHD Other cardiovascular disease All cancer All respiratory disease Other diseases All-causes All cardiovascular disease Stroke IHD Other cardiovascular disease All cancer All respiratory disease Other diseases
Self-comparative SRH
Better
Normal
Worse
Better
Normal
Worse
HR
HR
95% CI
HR
95% CI
HR
HR
95% CI
HR
95% CI
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1.07 1.16 1.22 1.15 1.12 0.92 1.34 1.15 1.09 1.14 1.21 1.08 1.16 1.00 1.16 1.09 1.04 0.96 0.93 0.78 1.40 1.38 0.97 1.02
1.02, 1.13 1.05, 1.29 1.02, 1.45 0.97, 1.35 0.91, 1.38 0.85, 1.00 1.16, 1.54 1.01, 1.30 1.04, 1.15 1.04, 1.26 1.02, 1.44 0.92, 1.25 0.97, 1.39 0.91, 1.11 1.04, 1.29 0.97, 1.22 0.93, 1.15 0.79, 1.17 0.66, 1.31 0.57, 1.06 0.94, 2.09 1.05, 1.81 0.80, 1.18 0.81, 1.28
1.35 1.38 1.52 1.34 1.27 1.05 2.18 1.41 1.30 1.36 1.40 1.31 1.38 1.11 1.37 1.40 0.96 1.11 1.03 0.88 1.73 1.02 0.82 0.91
1.25, 1.47 1.18, 1.62 1.17, 1.97 1.04, 1.72 0.92, 1.75 0.92, 1.21 1.80, 2.65 1.16, 1.70 1.19, 1.41 1.16, 1.58 1.07, 1.84 1.02, 1.67 1.03, 1.85 0.93, 1.32 1.15, 1.63 1.16, 1.68 0.79, 1.16 0.79, 1.55 0.55, 1.94 0.52, 1.51 0.94, 3.17 0.60, 1.72 0.57, 1.19 0.60, 1.38
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
0.82 0.81 0.75 0.82 0.90 0.87 0.79 0.75 0.89 0.86 0.91 0.91 0.76 0.96 0.88 0.87 0.85 0.97 0.93 0.97 1.01 0.70 0.87 0.86
0.76, 0.89 0.70, 0.94 0.59, 0.97 0.65, 1.04 0.66, 1.21 0.77, 0.99 0.65, 0.96 0.62, 0.89 0.82, 0.97 0.74, 1.00 0.69, 1.19 0.71, 1.17 0.58, 1.00 0.80, 1.15 0.74, 1.06 0.71, 1.05 0.70, 1.04 0.66, 1.40 0.50, 1.75 0.53, 1.77 0.49, 2.09 0.46, 1.07 0.60, 1.26 0.56, 1.32
0.89 0.82 0.90 0.78 0.76 0.96 0.91 0.81 0.93 0.84 0.87 0.86 0.79 1.03 0.98 0.93 0.79 0.89 0.74 0.94 1.02 0.66 0.76 0.84
0.82, 0.96 0.70, 0.95 0.70, 1.16 0.61, 0.99 0.55, 1.05 0.84, 1.10 0.74, 1.11 0.68, 0.98 0.85, 1.02 0.72, 0.98 0.66, 1.16 0.66, 1.11 0.60, 1.05 0.86, 1.23 0.81, 1.18 0.76, 1.13 0.65, 0.97 0.60, 1.30 0.39, 1.41 0.51, 1.73 0.48, 2.14 0.43, 1.03 0.52, 1.12 0.55, 1.30
Adjusted for age in years, sex, education, monthly expenditure, housing type, alcohol use, smoking, exercise, BMI, depression and objective health status.
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received or disease occurrence over the years of follow-up, which may mediate the association of SRH with mortality but not confound the association of SRH with mortality. Our question concerns the association of SRH with mortality rather than trajectories of health service use or the process by which poor SRH leads to mortality. Accessible high quality medical care is provided for all residents of Hong Kong (Department of Health, 2014), making it unlikely that poor SRH leads to mortality via differential health care utilization, although we cannot rule out the possibility that lack of health literacy may mediate the process by which SRH leads to mortality, and as such could be a potential target of intervention along with many social determinants of health. However, we did not find that the association of SRH with mortality varied with socioeconomic position, which might be an indicator of differential access to care or differential self-management. On the contrary the equitable access to care in Hong Kong (Department of Health, 2014) may relate to the lack of variation in the association of SRH with mortality by socioeconomic position. Our findings for age-comparative SRH are generally consistent with those in people of the same age with similar follow-up in the West, where worse age-comparative SRH is associated with a higher risk of death from all-causes, cardiovascular disease and respiratory disease, but not associated with death from cancer (Appels et al., 1996; Fernández-Ruiz et al., 2013; Sargent-Cox et al., 2010; Vuorisalmi et al., 2005). However, the magnitude of the association of age-comparative SRH with death from all- and specific causes in our setting is smaller than that in Western settings. Our findings of no difference in association of SRH with death by socioeconomic position are not inconsistent with studies from the West. People with more education might have a better appreciation of their health status. Accordingly, several studies from the West have found a stronger association for people with more education (Dowd and Zajacova, 2007; Huisman et al., 2007). However, humans are not particularly rational actors, and other studies have found stronger associations in people with less education (Singh-Manoux et al., 2007) or no variation by education (Van Doorslaer and Gerdtham, 2003). Studies concerning the association of SRH with death by income or occupation are similarly mixed (Burström and Fredlund, 2001; Singh-Manoux et al., 2007; Van Doorslaer and Gerdtham, 2003). Correspondingly, why some studies have found a stronger association in more advantaged socioeconomic groups is unclear as the characteristics of participants and follow-up duration were not substantially different. Nevertheless, age-comparative SRH may be a valid predictor of death across different socioeconomic groups in our non-Western setting. There are several explanations for the small magnitude of the association of SRH with mortality. First, in the West, the leading cause of death is cardiovascular disease (Lozano et al., 2013) but it is cancer in Hong Kong (Department of Health, 2012). SRH is less strongly associated with death from cancer than from cardiovascular disease (FernándezRuiz et al., 2013), thus more deaths from cancer may lead to a weaker association. Second, Hong Kong has long life expectancy (United Nations, 2013), so at any given age, Hong Kong people have longer to live than Westerners, when SRH is a better predictor of death in the short- than long-term. Third, people in the West may be more likely to report better age-comparative SRH (Sargent-Cox et al., 2010; Vuorisalmi et al., 2005) while people in our setting may be more “cautious” because moderation is favored in Chinese culture, which warns one to be vigilant when beyond others (Chen and Ma, 2002). Thus Chinese people may report “normal” SRH even when they are in good health. On the other hand, older people may be more superstitious, particularly in China, so they might be less willing to report poor health for fear of bringing bad luck and bad health (Li, 2011). Moreover, our participants were less likely to be current smokers or moderate drinkers than older people from the West (Fernández-Ruiz et al., 2013). As such, SRH may have less discrimination in Chinese people thereby weakening the association of age-comparative SRH with death. Fourth, older Chinese may be more likely to report non-fatal illness than people
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in the West (Sadana et al., 2000), which may also result in the smaller magnitude of association. Our study found that the association of age-comparative SRH with death from stroke varied by sex, with the association stronger for men than women. Given that stroke usually occurs at younger ages for men than women (Appelros et al., 2009), age-adjusted baseline agecomparative SRH may be a better predictor for men. The much weaker association of age-comparative SRH with death from all-causes in participants aged ≥85 years could be due to inaccurate estimation of health status because of cognitive problems. In contrast, worse self-comparative SRH was not associated with higher risk of death, consistent with previous studies (Bath, 2003; Deeg and Kriegsman, 2003; Fernández-Ruiz et al., 2013; Sargent-Cox et al., 2010). The association did not vary by age-comparative SRH. The distribution of self-comparative SRH differed from that of age-comparative SRH with most participants reporting normal or worse self-comparative SRH. Better age-comparative SRH may be an indication of good health, but better self-comparative SRH may reflect temporary amelioration of chronic diseases and symptoms. Self-comparative SRH has a U-shaped relation with several health indices (Li et al., 2006), which may underlie the lower risks of death from all- and specific causes for those with normal self-comparative SRH. Besides, older people may lower their standard for a healthy state and those with objectively “poor health” often rate their health as good (King, 2002). Conclusion In Hong Kong, the most westernized city of China, age-comparative SRH predicted death among older people although the magnitude of association was smaller than that in Western populations, possibly because of a different cause-composition of mortality, long life expectancy or contextually specific assessments of health. Consistent with Western studies, age-comparative SRH also predicted death from cardiovascular and respiratory diseases more strongly than death from cancer. The association of age-comparative SRH with death did not vary by socioeconomic position. In contrast, worse self-comparative SRH did not predict higher mortality. Conflict of interest The authors declares that there is no competing interests. Acknowledgments We wish to thank the staff of the Elderly Health Centers and the Hospital Authority for their assistance in data collection and entry. References Alfonso, H., Beer, C., Yeap, B.B., Hankey, G.J., Flicker, L., Almeida, O.P., 2012. Perception of worsening health predicts mortality in older men: the Health in Men Study (HIMS). Arch. Gerontol. Geriatr. 55, 363–368. Altman, D.G., Bland, J.M., 2003. Interaction revisited: the difference between two estimates. BMJ 326, 219. Appelros, P., Stegmayr, B., Terént, A., 2009. Sex differences in stroke epidemiology: a systematic review. Stroke 40, 1082–1090. Appels, A., Bosma, H., Grabauskas, V., Gostautas, A., Sturmans, F., 1996. Self-rated health and mortality in a Lithuanian and a Dutch population. Soc. Sci. Med. 42, 681–689. Bath, P.A., 2003. Differences between older men and women in the self-rated health— mortality relationship. The Gerontologist 43, 387–395. Burström, B., Fredlund, P., 2001. Self rated health: is it as good a predictor of subsequent mortality among adults in lower as well as in higher social classes? J. Epidemiol. Community Health 55, 836–840. Chen, G., Ma, R., 2002. The impact of harmony on Chinese conflict management. Chin. Confl. Manag. Resolut. 3–17. Cotter, K.A., Lachman, M.E., 2010. Psychosocial and behavioural contributors to health: age-related increases in physical disability are reduced by physical fitness. Psychol. Health 25, 805–820. de Bruin, A., Picavet, H.S., Nossikov, A., 1996. Health interview surveys: towards international harmonization of methods and instruments. WHO Reg. Publ. Eur. Ser. 58, i-xiii, pp. 1–161.
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