Journal of Aging and Health http://jah.sagepub.com/
Association Between 6-Minute Walk Test and All-Cause Mortality, Coronary Heart Disease−Specific Mortality, and Incident Coronary Heart Disease Ali Yazdanyar, Michael M. Aziz, Paul L. Enright, Daniel Edmundowicz, Robert Boudreau, Kim Sutton-Tyrell, Lewis Kuller and Anne B. Newman J Aging Health published online 2 April 2014 DOI: 10.1177/0898264314525665 The online version of this article can be found at: http://jah.sagepub.com/content/early/2014/04/01/0898264314525665
Published by: http://www.sagepublications.com
Additional services and information for Journal of Aging and Health can be found at: Email Alerts: http://jah.sagepub.com/cgi/alerts Subscriptions: http://jah.sagepub.com/subscriptions Reprints: http://www.sagepub.com/journalsReprints.nav Permissions: http://www.sagepub.com/journalsPermissions.nav
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525665 research-article2014
JAHXXX10.1177/0898264314525665Journal of Aging and HealthYazdanyar et al.
Article
Association Between 6-Minute Walk Test and All-Cause Mortality, Coronary Heart Disease–Specific Mortality, and Incident Coronary Heart Disease
Journal of Aging and Health 1–17 © The Author(s) 2014 Reprints and permissions: sagepub.com/journalsPermissions.nav DOI: 10.1177/0898264314525665 jah.sagepub.com
Ali Yazdanyar, DO, PhD1, Michael M. Aziz, MD, MPH2, Paul L. Enright, MD3, Daniel Edmundowicz, MD, MS4, Robert Boudreau, PhD5, Kim Sutton-Tyrell, DrPH5, Lewis Kuller, MD, DrPH5, and Anne B. Newman, MD, MPH5
Abstract Objective: To examine the association between 6-min walk test (6 MWT) performance and all-cause mortality, coronary heart disease mortality, and incident coronary heart disease in older adults. Method: We conducted a time-to-event analysis of 1,665 Cardiovascular Health Study participants 1Reading
Health System, West Reading, PA, USA Health System, Morristown, NJ, USA 3University of Arizona, Tuscon, USA 4Temple University, Philadelphia, PA, USA 5University of Pittsburgh, PA, USA 2Atlantic
Corresponding Author: Ali Yazdanyar, Section of Hospital Medicine, Department of Medicine, Reading Health System, Sixth Avenue and Spruce Street, West Reading, PA 19612, USA. Email: [email protected]
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without prevalent cardiovascular disease with a 6 MWT. Results: During a mean follow-up of 8 years, there were 305 incident coronary heart disease events, and 504 deaths of which 100 were coronary heart disease–related deaths. The 6 MWT performance in the shortest two distance quintiles was associated with increased risk of all-cause mortality (290-338 m: hazard ratio [HR] = 1.7; 95% confidence interval [CI] = [1.2, 2.5]; 414 m) served as the referent group. Crude event rates were calculated and reported per 1,000 person-years. Cox proportional hazard regression was used to estimate hazard ratios (HRs) and event rates (per 1,000 person-years). Kaplan–Meier analysis was used to evaluate differences in study endpoints between the 6 MWT distance quintiles. Multivariable models included controls for age and sex, and subsequently for other covariates. To evaluate discrimination and improvement imparted by 6 MWT, we compared the adjusted model without 6 MWT (Model A) to adjusted model with the 6 MWT (Model B). Discrimination, the ability of two models to distinguish participants who develop a study endpoint from those who do not, was evaluated by Harrell’s C statistic. We calculated
Downloaded from jah.sagepub.com at National Dong Hwa University on April 9, 2014
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Journal of Aging and Health
category-free Net Reclassification Improvement (NRI) and Integrated Discrimination Improvement (IDI) to evaluate the improvement imparted by the addition of 6 MWT to Model A. All reported p values are based on a twosided test, with p value < .05 being considered statistically significant. Statistical analysis was performed using STATA MP 11.1 (StataCorp, College Station, Texas).
Results There were 1,665 participants without prevalent cardiovascular disease among the 2,279 who attempted a 6 MWT with a mean age of 77 years. The participants were predominantly women (65%) and less likely to be of nonWhite race (15%). The mean 6 MWT distance was 349 m. As displayed in Table 1, participants with longer 6 MWT distance performance had a more favorable characteristic profile such as younger age, lower body mass index, less likely to have limitations in IADL and ADLs, or to have arthritis of knees or hips.
6 MWT Distance and Mortality There were 504 deaths among the 1,665 of the 2,279 participants without prevalent cardiovascular disease who attempted a 6 MWT (Table 2). Figure 1shows the all-cause mortality Kaplan–Meier Survival curve by 6 MWT distance quintiles. Among the participants with a 6 MWT, a distance in the two shortest distance quintiles (walk distance 290-338 m and 414 m. The increased risk of all-cause mortality remained in age and sex-adjusted models. In a fully adjusted model, a 6 MWT distance in the shortest two performance quintiles remained associated with an increased risk of all-cause mortality. The adjusted risk of all-cause mortality was progressively higher with decreasing 6 MWT distance. Age- and sex-stratified analyses revealed a similar inverse association between 6 MWT performance and all-cause mortality (Table 3). Both older aged men and women who walked less than 338 m were at increased risk of all-cause mortality. The association between 6 MWT distance and mortality differed between White and non-White participants, with a significant association only observed among the White participants. Due to the small sample size of non-White participants with a 6 MWT, the lack of association among non-White participants should be interpreted with caution. Table 4 displays results of the tests of discrimination and reclassification for the models with and without 6 MWT. The addition of 6 MWT to the
Downloaded from jah.sagepub.com at National Dong Hwa University on April 9, 2014
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Yazdanyar et al.
Table 1. Characteristics by Distance Quintiles (Range in Parentheses) of 6-Min Walk Test Performance (m) Among Participants Without Prevalent Cardiovascular Disease. Characteristics Age, year Male Non-White Education BMI, kg/m2 SBP Diabetes Arthritis Pulmonary disease ADL limitation IADL limitation Current smoking Fair/poor health CES-Depression Mini-MMSE Major ECG AAI (414) (n = 333)
(373-414) (n = 332)
(338-373) (n = 334)
(290-338) (n = 327)
(0-290) (n = 339)
p value
76.2 ± 3.4 160 (48.1) 24 (7.2) 37 (11.1) 25.7 ± 3.4 133 ± 18 20 (6.0) 69 (22.0) 41 (12.8) 16 (4.8) 34 (10.2) 13 (3.9) 12 (3.6) 4.2 ± 4.0 96.0 ± 4.9 67 (20.2) 16 (5.0) 198 ± 36.6 99 ± 23.3 1.5 (.8,3.3)
76.6 ± 3.8 128 (38.6) 40 (12.1) 62 (18.7) 26.4 ± 3.8 136 ± 18 41 (12.4) 61 (19.6) 29 (9.0) 27 (8.1) 51 (15.4) 17 (5.2) 21 (6.4) 4.6 ± 4.1 94.1 ± 6.8 65 (19.8) 23 (7.1) 203 ± 38.2 102 ± 25.8 2.1 (1.1,2.1)
77.1 ± 4.2 116 (34.7) 59 (17.7) 79 (23.7) 26.7 ± 3.8 136 ± 19 35 (10.5) 79 (24.7) 27 (8.3) 28 (8.5) 61 (18.3) 30 (9.0) 37 (11.1) 5.1 ± 4.2 93.4 ± 7.0 74 (22.8) 31 (9.8) 205 ± 37.5 103 ± 26.6 2.4 (1.2,5.5)
77.7 ± 4.2 97 (29.7) 57 (17.4) 80 (24.5) 27.5 ± 4.6 137 ± 19 33 (10.1) 118 (37.6) 47 (15.0) 40 (12.3) 101 (31.0) 22 (6.9) 44 (13.6) 5.3 ± 4.5 92.5 ± 7.8 77 (23.8) 49 (16.1) 207 ± 36.2 103 ± 24.8 2.7 (1.3,6.0)
78.7 ± 5.0 83 (24.5) 73 (21.5) 102 (30.0) 27.7 ± 5.4 139 ± 22 50 (14.8) 125 (37.9) 58 (17.8) 62 (18.9) 122 (36.0) 30 (9.2) 63 (18.8) 5.9 ± 4.5 90.8 ± 9.0 92 (27.4) 76 (23.5) 205 ± 42.0 104 ± 25.6 2.9 (1.3,5.7)
Association Between 6-Minute Walk Test and All-Cause Mortality, Coronary Heart Disease−Specific Mortality, and Incident Coronary Heart Disease Ali Yazdanyar, Michael M. Aziz, Paul L. Enright, Daniel Edmundowicz, Robert Boudreau, Kim Sutton-Tyrell, Lewis Kuller and Anne B. Newman J Aging Health published online 2 April 2014 DOI: 10.1177/0898264314525665 The online version of this article can be found at: http://jah.sagepub.com/content/early/2014/04/01/0898264314525665
Published by: http://www.sagepublications.com
Additional services and information for Journal of Aging and Health can be found at: Email Alerts: http://jah.sagepub.com/cgi/alerts Subscriptions: http://jah.sagepub.com/subscriptions Reprints: http://www.sagepub.com/journalsReprints.nav Permissions: http://www.sagepub.com/journalsPermissions.nav
>> OnlineFirst Version of Record - Apr 2, 2014 What is This?
Downloaded from jah.sagepub.com at National Dong Hwa University on April 9, 2014
525665 research-article2014
JAHXXX10.1177/0898264314525665Journal of Aging and HealthYazdanyar et al.
Article
Association Between 6-Minute Walk Test and All-Cause Mortality, Coronary Heart Disease–Specific Mortality, and Incident Coronary Heart Disease
Journal of Aging and Health 1–17 © The Author(s) 2014 Reprints and permissions: sagepub.com/journalsPermissions.nav DOI: 10.1177/0898264314525665 jah.sagepub.com
Ali Yazdanyar, DO, PhD1, Michael M. Aziz, MD, MPH2, Paul L. Enright, MD3, Daniel Edmundowicz, MD, MS4, Robert Boudreau, PhD5, Kim Sutton-Tyrell, DrPH5, Lewis Kuller, MD, DrPH5, and Anne B. Newman, MD, MPH5
Abstract Objective: To examine the association between 6-min walk test (6 MWT) performance and all-cause mortality, coronary heart disease mortality, and incident coronary heart disease in older adults. Method: We conducted a time-to-event analysis of 1,665 Cardiovascular Health Study participants 1Reading
Health System, West Reading, PA, USA Health System, Morristown, NJ, USA 3University of Arizona, Tuscon, USA 4Temple University, Philadelphia, PA, USA 5University of Pittsburgh, PA, USA 2Atlantic
Corresponding Author: Ali Yazdanyar, Section of Hospital Medicine, Department of Medicine, Reading Health System, Sixth Avenue and Spruce Street, West Reading, PA 19612, USA. Email: [email protected]
Downloaded from jah.sagepub.com at National Dong Hwa University on April 9, 2014
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Journal of Aging and Health
without prevalent cardiovascular disease with a 6 MWT. Results: During a mean follow-up of 8 years, there were 305 incident coronary heart disease events, and 504 deaths of which 100 were coronary heart disease–related deaths. The 6 MWT performance in the shortest two distance quintiles was associated with increased risk of all-cause mortality (290-338 m: hazard ratio [HR] = 1.7; 95% confidence interval [CI] = [1.2, 2.5]; 414 m) served as the referent group. Crude event rates were calculated and reported per 1,000 person-years. Cox proportional hazard regression was used to estimate hazard ratios (HRs) and event rates (per 1,000 person-years). Kaplan–Meier analysis was used to evaluate differences in study endpoints between the 6 MWT distance quintiles. Multivariable models included controls for age and sex, and subsequently for other covariates. To evaluate discrimination and improvement imparted by 6 MWT, we compared the adjusted model without 6 MWT (Model A) to adjusted model with the 6 MWT (Model B). Discrimination, the ability of two models to distinguish participants who develop a study endpoint from those who do not, was evaluated by Harrell’s C statistic. We calculated
Downloaded from jah.sagepub.com at National Dong Hwa University on April 9, 2014
6
Journal of Aging and Health
category-free Net Reclassification Improvement (NRI) and Integrated Discrimination Improvement (IDI) to evaluate the improvement imparted by the addition of 6 MWT to Model A. All reported p values are based on a twosided test, with p value < .05 being considered statistically significant. Statistical analysis was performed using STATA MP 11.1 (StataCorp, College Station, Texas).
Results There were 1,665 participants without prevalent cardiovascular disease among the 2,279 who attempted a 6 MWT with a mean age of 77 years. The participants were predominantly women (65%) and less likely to be of nonWhite race (15%). The mean 6 MWT distance was 349 m. As displayed in Table 1, participants with longer 6 MWT distance performance had a more favorable characteristic profile such as younger age, lower body mass index, less likely to have limitations in IADL and ADLs, or to have arthritis of knees or hips.
6 MWT Distance and Mortality There were 504 deaths among the 1,665 of the 2,279 participants without prevalent cardiovascular disease who attempted a 6 MWT (Table 2). Figure 1shows the all-cause mortality Kaplan–Meier Survival curve by 6 MWT distance quintiles. Among the participants with a 6 MWT, a distance in the two shortest distance quintiles (walk distance 290-338 m and 414 m. The increased risk of all-cause mortality remained in age and sex-adjusted models. In a fully adjusted model, a 6 MWT distance in the shortest two performance quintiles remained associated with an increased risk of all-cause mortality. The adjusted risk of all-cause mortality was progressively higher with decreasing 6 MWT distance. Age- and sex-stratified analyses revealed a similar inverse association between 6 MWT performance and all-cause mortality (Table 3). Both older aged men and women who walked less than 338 m were at increased risk of all-cause mortality. The association between 6 MWT distance and mortality differed between White and non-White participants, with a significant association only observed among the White participants. Due to the small sample size of non-White participants with a 6 MWT, the lack of association among non-White participants should be interpreted with caution. Table 4 displays results of the tests of discrimination and reclassification for the models with and without 6 MWT. The addition of 6 MWT to the
Downloaded from jah.sagepub.com at National Dong Hwa University on April 9, 2014
7
Yazdanyar et al.
Table 1. Characteristics by Distance Quintiles (Range in Parentheses) of 6-Min Walk Test Performance (m) Among Participants Without Prevalent Cardiovascular Disease. Characteristics Age, year Male Non-White Education BMI, kg/m2 SBP Diabetes Arthritis Pulmonary disease ADL limitation IADL limitation Current smoking Fair/poor health CES-Depression Mini-MMSE Major ECG AAI (414) (n = 333)
(373-414) (n = 332)
(338-373) (n = 334)
(290-338) (n = 327)
(0-290) (n = 339)
p value
76.2 ± 3.4 160 (48.1) 24 (7.2) 37 (11.1) 25.7 ± 3.4 133 ± 18 20 (6.0) 69 (22.0) 41 (12.8) 16 (4.8) 34 (10.2) 13 (3.9) 12 (3.6) 4.2 ± 4.0 96.0 ± 4.9 67 (20.2) 16 (5.0) 198 ± 36.6 99 ± 23.3 1.5 (.8,3.3)
76.6 ± 3.8 128 (38.6) 40 (12.1) 62 (18.7) 26.4 ± 3.8 136 ± 18 41 (12.4) 61 (19.6) 29 (9.0) 27 (8.1) 51 (15.4) 17 (5.2) 21 (6.4) 4.6 ± 4.1 94.1 ± 6.8 65 (19.8) 23 (7.1) 203 ± 38.2 102 ± 25.8 2.1 (1.1,2.1)
77.1 ± 4.2 116 (34.7) 59 (17.7) 79 (23.7) 26.7 ± 3.8 136 ± 19 35 (10.5) 79 (24.7) 27 (8.3) 28 (8.5) 61 (18.3) 30 (9.0) 37 (11.1) 5.1 ± 4.2 93.4 ± 7.0 74 (22.8) 31 (9.8) 205 ± 37.5 103 ± 26.6 2.4 (1.2,5.5)
77.7 ± 4.2 97 (29.7) 57 (17.4) 80 (24.5) 27.5 ± 4.6 137 ± 19 33 (10.1) 118 (37.6) 47 (15.0) 40 (12.3) 101 (31.0) 22 (6.9) 44 (13.6) 5.3 ± 4.5 92.5 ± 7.8 77 (23.8) 49 (16.1) 207 ± 36.2 103 ± 24.8 2.7 (1.3,6.0)
78.7 ± 5.0 83 (24.5) 73 (21.5) 102 (30.0) 27.7 ± 5.4 139 ± 22 50 (14.8) 125 (37.9) 58 (17.8) 62 (18.9) 122 (36.0) 30 (9.2) 63 (18.8) 5.9 ± 4.5 90.8 ± 9.0 92 (27.4) 76 (23.5) 205 ± 42.0 104 ± 25.6 2.9 (1.3,5.7)
