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Work-Related Psychosocial Risk Factors for Long-Term Sick Leave A Prospective Study of the General Working Population in Norway Cecilie Aagestad, MSc, H˚akon A. Johannessen, PhD, Tore Tynes, MD, PhD, Hans Magne Gravseth, MD, PhD, and Tom Sterud, PhD Objective: To examine the effect of work-related psychosocial exposures on long-term sick leave (LTSL) in the general working population. Methods: A prospective study of the general working population in Norway. Eligible respondents were interviewed in 2009 and registered with at least 100 working days in 2009 and 2010 (n = 6758). The outcome was medically confirmed LTSL of 40 days or more during 2010. Results: In the fully adjusted model, high exposure to role conflict (odds ratio [OR], 1.58; 95% confidence interval [CI], 1.20 to 2.09), emotional demands (OR, 1.32; 95% CI, 1.03 to 1.69), and low supportive leadership (OR = 1.50; 95% CI, 1.15 to 1.96) predicted LTSL. A test for trend was statistically significant for all factors (P ≤ 0.05). We estimated that 15% of LTSL cases were attributable to these factors. Conclusions: This study underlines the importance of taking into account psychosocial exposures as risk factors for LTSL.
S
ick leave generates considerable public financial costs to society, and expenditures are high in the Nordic countries and highest in Norway.1 Several studies have found that stressful characteristics at work predict sick leave2–5 ; however, uncertainty persists about which factors in the psychosocial work environment have the greatest effect on sick leave. Identifying these factors may help prevent individual ill-health and reduce economic costs for society. The main focus in most previous studies has been the importance of the job demand–control (social support) model as a predictor for sick leave.4,6 The job strain model suggests that high job demands will have the greatest adverse effect on health in those with low job control.7,8 In a 2004 systematic review, low job control seemed to be the best documented risk factor for increased sickness absence.4 The effect of high demand, social support, and the combination of high job demands and low control (job strain) was not conclusive, though, and few studies had addressed other workrelated psychosocial factors.4 In more recent studies taking a wider range of psychosocial factors into account, “new” factors like emotional demands, role conflict, and quality of leadership emerged as potentially important for long-term sick leave (LTSL).9,10 Overall, however, the evidence for most work-related psychosocial factors remains limited or inconclusive. Assessment of the relationships between work-related psychosocial factors and LTSL thus remains a topic of interest. Few studies have taken multiple psychosocial factors into account when From the Department of Occupational Health Surveillance (Ms Aagestad and Drs Johannessen, Tynes, Gravseth, and Sterud), National Institute of Occupational Health, Oslo; and Department of Behavioral Sciences (Ms Aagestad), Institute of Basic Medical Sciences, Faculty of Medicine, University of Oslo, Norway. Authors Aagestad, Johannessen, Tynes, Gravseth, and Sterud have no relationships/conditions/circumstances that present potential conlict of interest. The JOEM editorial board and planners have no financial interest related to this research. Address correspondence to: Cecilie Aagestad, MSc, Department of Occupational Health Surveillance, National Institute of Occupational Health, PO Box 8149 Dep, NO-0033 Oslo, Norway ([email protected]). C 2014 by American College of Occupational and Environmental Copyright Medicine DOI: 10.1097/JOM.0000000000000212
Learning Objectives
r Summarize the new findings on work-related psychosocial r r
exposures associated with the risk of long-term sick leave in Norwegian workers. Identify the estimated fractions of long-term sick leave cases attributable to psychosocial factors. Discuss the potential implications for interventions to reduce long-term sick leave in the general population.
studying LTSL, and few have considered the potential confounding of mechanical factors.2,11–13 In addition, most recent national-level studies on medically confirmed LTSL and psychosocial risk factors have been conducted in Denmark, and these findings remain to be confirmed in other nationally representative population studies. By combining data on prevalence and risk, this study enables us to estimate the proportion of LTSL cases in the population attributable to psychosocial exposures at work. Only a few former studies have provided such information.14,15 The aim of this article was, therefore, to identify the psychosocial factors with the greatest effect on LTSL. We tested the effect of a wide range of work-related psychosocial factors in a randomly selected prospective cohort from the general working-age population in Norway. Potential confounders such as age, sex, cohabitation, children living at home, education, occupation, previous high level of sick leave, chronic health condition, disability, smoking, and mechanical working conditions were taken into account.
STUDY POPULATION AND METHODS Data were provided from the nationwide survey of living conditions/work environment, conducted by Statistics Norway. Data were collected during the period June 22, 2009, to January 9, 2010, by personal telephone interviews (0.5% of completed interviews were face to face). Prior to telephone contact, potential respondents were informed by mail about the study, the topic of the study, and data/privacy protection.
Population Eligible respondents were community-living Norwegian residents aged 18 to 69 years. In 2009, a gross sample of 20,136 was randomly drawn from this population. Of these, a total of 12,255 persons were interviewed (60.9%). The baseline sample was compared with the gross sample according to the benchmarks of age, sex, and region, and no major differences were detected (Table 1).16 Data on sick leave were obtained by a merger between the survey of living conditions/work environment and the national registry of social transfer payments. The registry includes all economically active individuals aged 16 to 69 years in Norway (ie, those with a minimum of 4 hours per average working week) in the reference period. Respondents who were in paid work for at least 1 hour during the reference week or temporarily absent from such work and had
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TABLE 1. Gross Sample, Baseline Sample and the Difference in Percentage Points Between Baseline and Gross Sample According to Sex, Age, and Region (Percentage)
N Sex Male Female Age, yrs 16–24 25–44 45–66 ≥67 Region Akershus and Oslo Hedmark and Oppland Rest of Southeast Norway Agder and Rogaland Western Norway Mid Norway North Norway
Gross Sample
Baseline Sample
Dropouts
20,136
12,255
7,881
51.7 48.3
50.2 49.8
51.4 45.9
− 1.5 1.5
13.3 41.2 42.2 3.3
13.0 38.5 44.9 3.7
13.9 45.3 38.1 2.7
− 0.3 − 2.7 2.7 0.4
24 7.7 18.6 14.4 16.8 9.2 9.4
23.4 7.8 18.1 14.6 17.1 9.6 9.3
24.7 7.4 19.5 14.1 16.4 8.5 9.5
− 0.6 0.1 − 0.5 0.2 0.3 0.4 − 0.1
worked for at least 100 actual working days during a year both in 2009 and 2010 constituted the follow-up sample in this article (n = 6758).
Sick Leave Long-term sick leave was defined as medically confirmed sick leave for a period of 40 or more actual working days (ie, 8 weeks or more) during 2010, the year after the initial survey was undertaken. A similar definition of LTSL has been applied in other studies.14,17,18
Risk Factors Psychosocial risk factors were measured with six scales and two single items. A Cronbach α was estimated for each included scale. Quantitative demands at work was measured with the following two items from The General Nordic Questionnaire for Psychological and Social Factors at Work (QPS)19 (α = 0.70): (1) “How often is it necessary to work at a rapid pace?” and (2) “How often do you have too much to do?” Answer categories were “very seldom or never,” “rather seldom,” “sometimes,” “rather often,” and “very often or always.” Role conflict was measured with the following three items from QPS19 (α = 0.64): (1) “How often do you receive incompatible requests from two or more people?”; (2) “How often are you given assignments without adequate resources to complete them?”; and (3) “How often do you have to do things that you feel should be done differently?” Answer categories were “very seldom or never,” “rather seldom,” “sometimes,” “rather often,” and “very often or always.” Supportive leadership was measured with the following three items from QPS19 (α = 0.70): (1) “If needed, how often can you get support and help from your immediate superior with your work?”; (2) “ Are your work achievements appreciated by your immediate superior?”; and (3) “Does your immediate superior treat employees fairly and equally?” Answer categories were “very seldom or never,” “rather seldom,” “sometimes,” “rather often,” and “very often or always.” Job control was measured with two questions from QPS19 and two questions developed by Statistics Norway16 (α = 0.71) as follows: (1) “To what extent can you set your own work pace”; (2) “To what extent can you influence decisions that are important for your work?”; (3) “To what extent are you free to decide how to go about your work?”; and (4) “To what extent are you free to decide 788
Difference
your own tasks?” Answer categories were “to a very great extent,” “to a great extent,” “to some extent,” “not really,” and “hardly at all.” For these work-related psychosocial factors, the five-point scale score was converted into the following three categories: low (1.0 to 2.0), medium (2.1 to 3.0), and high (3.1 to 5.0). By dichotomizing job control (low = 1, medium and high = 0) and quantitative demands (high = 1, medium and low = 0), we constructed a job strain variable—low strain (job control = 0, quantitative demands = 0); passive (job control = 1, quantitative demands = 0); active (job control = 0, quantitative demands = 1); and high strain (job control = 1, quantitative demands = 1). Low strain was set as the reference value. Emotional demands was measured with the following two items developed by Statistics Norway16 (α = 0.69): (1) “In your work, to what extent do you need to deal with strong feelings such as sorrow, anger, desperation, frustration, and so on from customers, clients, or other people who are not employed at your workplace?” Answer categories were “to a very great extent, “to a great extent,” “to some extent,” “not really,” and “not at all”; and (2) “In your work, to what extent do you need to conceal negative feelings such as anger, irritation, frustration, and so on for customers, clients, or other people who are not employed at your workplace?” Answer categories were “to a great extent,” “to some extent,” “not really,” and “not at all.” For these work-related psychosocial factors, the mean scale score was converted into the following three categories: low (1.0 to 2.0), medium (2.1 to 3.0), and high (3.1 to 5.0). All variables were coded so that high exposures indicate assumed negative exposure such as high quantitative demands, high role conflict, high emotional demands, high job strain, low job control, and low supportive leadership. Possibilities for development (reversed) was measured with the following two items developed by Statistics Norway16 (α = 0.72): “In your job, how good are your opportunities to” (1) “develop your skills in the areas that interest you”; and (2) “make use of the skills, knowledge, and experience that you have gained through your education and past work?” Answer categories were “very good,” “good,” “poor,” and “very poor.” The last two categories were combined and used as one category, “poor or very poor.” Bullying was measured with the following two items developed by Statistics Norway: “Do you yourself sometimes get bothered or teased in an unpleasant way by your colleagues?” and “Do you yourself sometimes get bothered
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JOEM r Volume 56, Number 8, August 2014
or teased in an unpleasant way by superiors?” Answer categories were “yes, once or more a week,” “yes, once or more a month,” and “no.” The question and answer categories were computed into one dichotomous variable (yes = 1, no = 0). Job insecurity was measured with the following one item developed by Statistics Norway16 : “Do you believe that you are at risk of losing your job due to your company’s closing, downsizing, or other reasons over the coming 3 years?” Answer categories were “yes, due to its closing,” “yes, due to downsizing,” “yes, for other reasons,” and “no.” The categories were recoded into one dichotomous variable (yes = 1, no = 0). Potential confounders such as sex, age, and educational level were based on administrative registry data. Education was coded into five educational levels. Married/registered partner/cohabiting was coded as yes = 1, no = 0, as was children in the household. Occupation was based on an open questionnaire and coded by Statistics Norway into a professional title in accordance with the International Standard Classification of Occupations–88 and recoded into 10 occupational groups based on one-digit codes. Chronic health problem was measured with a single item as follows: “Do you have any long-term illnesses or health problems? This includes any illnesses or problems that are seasonal, or that are intermittent. The prerequisite is that the condition must have lasted, or be expected to last, at least 6 months.” Disability was measured with a single item as follows: “Are you disabled, or do you suffer pain as a result of an injury? This includes pains that are intermittent.” Smoking was measured with the following two items: “Do you sometimes smoke?” “Yes” respondents were asked, “Do you smoke every day or occasionally?” These variables were recoded into regular smokers versus non- or sometimes-smokers. Perceived mechanical workload was measured with the following seven items: neck flexion, hands above shoulders, hand/arm repetition, squatting/kneeling, standing, work with upper body bent forward, and awkward lifting, which have been shown to predict LTSL and are described in greater detail elsewhere.20 Scores were coded on a scale from 1 (not exposed or exposed very little of the work day) to 4 (exposed three fourths of the work day or more).
Statistics The associations between work environment and LTSL were calculated by logistic regression analyses as odds ratios (ORs) with 95% confidence intervals (CIs) with adjustment for potential confounders. In this study, medically confirmed sick leave days are registered for 1 year after the collection of survey data, and we have no information about the exact day of the interview or start and stop date for each sick leave episode. It was, therefore, not possible to conduct time-to-event analyses. On the contrary, it has been shown that if the follow-up period is short and the outcome is generally rare (when the probability of the event not occurring is close to 1), the regression coefficients of the logistic model approximate those of the proportional hazards model.21 Three models were evaluated. In model 1, we adjusted for sex, age, and registered LTSL in 2009. In model 2, further adjustments were made for educational level, cohabitation, children living at home, occupation, chronic health complaints, disabled/injured, and smoking. In model 3, further adjustments were made for work-related mechanical exposures. To limit the potential for overadjustment, each work-related psychosocial predictor was adjusted only for other work-related psychosocial predictors that were first estimated to exert an influence more than a certain threshold level. This estimation was made a priori, on the basis of the following procedure suggested by Rothman et al22 and applied to baseline data. In the first step, crude OR was separately estimated for each work-related factor. In the second step, each of the other work-related variables was entered one at a time. If the inclusion of a potential confounder resulted in a change in the OR of 10% or more, that variable was treated as a real confounder in the multiple regression models. We did additional separate analyses
Work-Related Psychosocial Risk Factors for Long-Term Sick Leave
for men and women in the fully adjusted model. Finally, to evaluate changes in the estimates, we did additional analyses among respondents with no LTSL registered in 2009. All statistical analyses were conducted with PASW Statistics package (formerly SPSS), version 20.0 (IBM, Armonk, NY). For statistically significant work-related factors in the regression analyses in the three models, we calculated the population attributable risk (PAR) estimates with 95% CI. In contrast to OR estimates, the PAR estimate combines data on prevalence and a measure of association to provide a quantitative estimate of the proportion of cases in the population that is attributable to a particular exposure. The method is described in detail by Natarajan et al.23 On the basis of the assumption that the predictors are statistically independent and no interaction exists between the effects of predictors on the outcome, the summary attributable risk in model 3 was calculated according to a mathematical formula described by Miettinen.24
RESULTS During the follow-up period, 635 (9.4%) were classified with LTSL. Table 2 describes the distribution of sociodemographic variables and health variables at baseline and the associated risk of LTSL at follow-up. The risk was significantly higher among women than among men (12.1% vs 7.2%, respectively), older workers (11.2% in the 55 to 69 years age group vs 8% to 9% in the other age groups), and those with lower education (13.9% for basic school level vs 3.8% for 4 years or older of university/college). A higher risk was also seen among those in elementary occupations (19.5% vs 4.9% for professionals), persons with a chronic health complaint (18.9% vs 6.7%), those who were disabled/injured (20% vs 8.3%), regular smokers (12.9% vs 8.6%), and those having LTSL during the baseline year (36.1% vs 6.9%). Civil status and children in the household were not related to LTSL. Table 3 shows the results of multiple logistic regression analyses with baseline psychosocial risk factors as the predictors and LTSL during the follow-up period as the outcome. In model 1 (adjusting for sick leave during the baseline year, age, and sex), significant associations with LTSL were found for high role conflict, high emotional demands, low supportive leadership, high job strain, low possibilities for development, low job control, and those reporting bullying. In model 2, low job control was close to significant. The main confounder was occupation. Possibilities for development were no longer a significant predictor when adjusted for occupation and education. Bullying was no longer a significant predictor when adjusted for work-related psychosocial confounders. In the fully adjusted model 3, significant predictors were high role conflict (OR, 1.58; 95% CI, 1.20 to 2.09), high emotional demands (OR, 1.32; 95% CI, 1.03 to 1.69), and low supportive leadership (OR, 1.50; 95% CI, 1.15 to 1.96). Job strain was close to significant. A test for linear trend was statistically significant for all three predictors in the model—role conflict (OR, 1.17; 95% CI, 1.05 to 1.30), emotional demands (OR, 1.37; 95% CI, 1.03 to 1.25), and supportive leadership (OR, 1.12; 95% CI, 1.02 to 1.23). In further analyses, we evaluated the effect of the single items included in each of these significant predictors separately. The estimates were rather consistent at singleitem level. Nevertheless, different estimates were observed for the two items constituting emotional demands (1) (OR, 1.16; 95% CI, 0.91 to 1.48) and (2) (OR, 1.49; 95% CI, 1.17 to 1.90). When we separately evaluated the risk for LTSL among men and women, most differences were small and not significant (P > 0.05). The largest difference detected was in high emotional demands for women (OR, 0.97; 95% CI, 0.71 to 1.33) and men (OR, 2.07; 95% CI, 1.36 to 3.16), (P ≤ 0.05). Moreover, when excluding respondents with LTSL in 2009 from the analyses, minor changes in the estimates were detected, with predictors being low supportive leadership (OR, 1.41; 95% CI, 1.03 to 1.92), high emotional demands (OR, 1.35; 95% CI, 1.01 to 1.80), and high role conflict (OR, 1.31; 95% CI,
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TABLE 2. Distribution of the Sociodemographic Variables and Health Variables at Baseline and the Associated Risk of LTSL During the Follow-Up Period
Total Age, yrs 17–24 25–34 35–44 45–54 55–69 Sex Male Female Education level Basic school level Upper secondary education, not finished Upper secondary education University/college 4 yrs University/college 4 yrs+ Missing Cohabitation Living alone Living with a partner Missing Children at home No Yes Missing Occupation Legislators, senior officials, and manager Professionals Technicians and associate professionals Clerks Service workers and shop and market sales workers Skilled agricultural and fishery workers Craft and related trades workers Plant and machine operators and assemblers Elementary occupations Other occupations Missing Chronic health complaints No Yes Missing Disabled/injured No Yes Missing Smoking No Yes Missing Long-term sick leave in 2009 No Yes
N
Cases (n*)
Cases, % (95% CI)
6,758
635
9.4 (8.70–10.10)
370 1,239 1,920 1,859 1,370
31 113 171 167 153
8.4 (5.57–11.23) 9.1 (7.50–10.70) 8.9 (7.63–10.17) 9.0 (7.70–10.30) 11.2 (9.53–12.87)
3,688 3,070
264 371
7.2 (6.37–8.03) 12.1 (10.95–13.25)
855 653 2,183 2,147 786 134
119 81 241 157 30
13.9 (11.30–15.90) 12.4 (9.87–14.93) 11.0 (9.69–12.31) 7.3 (6.20–8.40) 3.8 (2.46–5.14)
1,454 4,667 2
154 481
9.6 (8.14–11.02) 9.3 (8.55–10.14)
3,132 3,626 2
299 336
9.5 (8.52–10.58) 9.3 (8.32–10.21)
789 1,093 2,011 484 1,040 33 667 388 128 114 11
57 53 169 49 156 2 67 43 25 14
7.2 (5.40–9.00) 4.9 (3.62–6.18) 8.4 (7.19–9.61) 10.1 (7.42–12.78) 15.0 (12.83–17.17) 6.1 (−2.07–14.27) 10.0 (7.72–12.28) 11.1 (7.97–14.23) 19.5 (12.64–26.36) 12.3 (6.27–18.33)
5,232 1,504 22
348 284
6.7 (6.02–7.38) 18.9 (16.92–20.88)
5,595 508 22
504 127
8.3 (7.57–8.95) 20.0 (16.88–23.12)
5,482 1,252 24
470 162
8.6 (7.86–9.34) 12.9 (11.04–14.76)
6,182 576
427 208
6.9 (6.27–7.53) 36.1 (32.18–40.02)
*Long-term sick leave of 40 days or more during the follow-up.
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Work-Related Psychosocial Risk Factors for Long-Term Sick Leave
TABLE 3. Multiple Logistic Regression: LTSL During Follow-Up Regressed on Psychosocial Risk Factors Measured at Baselinea
Quantitative demands Low Medium High Job control High Medium Low Job strain Low strain Passive Active High strain Emotional demands Low Medium High Role conflict Low Medium High Supportive leadership High Medium Low Possibilities for development Very good Good Poor or very poor Bullying No Yes Job insecurity No Yes
N
Cases, n (%)
6,745 537 1,713 4,495 6,687 2,063 3,249 1,375 6,682 1,808 410 3,499 965 6,745 3,548 2,017 1,180 6,745 3,934 2,119 692 6,578 4,421 1,506 651 6,751 3,118 3,283 350 6,700 6,517 183 6,673 6,118 555
632 (9.4) 49 (9.1) 143 (8.3) 440 (9.8) 629 (9.4) 165 (8) 289 (8.9) 175 (12.7) 628 (9.4) 156 (8.6) 34 (8.3) 297 (8.5) 141 (14.6) 633 (9.4) 284 (8) 194 (9.6) 155 (13.1) 633 (9.4) 334 (8.5) 205 (9.7) 94 (13.6) 617 (9.4) 376 (8.5) 141 (9.4) 102 (15.7) 634 (9.4) 247 (7.9) 336 (10.2) 51 (14.6) 630 (9.4) 601 (9.2) 29 (15.8) 623 (9.3) 560 (9.2) 63 (11.4)
Model 1 OR (95% CI)b
Model 2 OR (95% CI)c
Model 3 OR (95%CI)d
1.00 0.95 (0.66–1.35) 1.10 (0.79–1.53)
1.00 0.99 (0.68–1.42) 1.21 (0.86–1.69)
1.00 0.94 (0.65–1.36) 1.06 (0.75–1.49)
1.00 1.05 (0.86–1.29) 1.36 (1.07–1.73) **
1.00 1.04 (0.83–1.29) 1.28 (0.99–1.65)
1.00 1.02 (0.81–1.27) 1.18 (0.91–1.52)
1.00 0.79 (0.53–1.19) 0.97 (0.78–1.20) 1.53 (1.18–1.99) *
1.00 0.78 (0.51–1.19) 1.04 (0.84–1.30) 1.50 (1.15–1.95)*
1.00 0.74 (0.49–1.14) 0.96 (O.77–1.20) 1.30 (0.99–1.71)
1.00 1.07 (0.87–1.31) 1.37 (1.20–1.72) **
1.00 1.08 (0.87–1.34) 1.39 (1.09–1.77) **
1.00 1.09 (0.88–1.35) 1.32 (1.03–1.69)*
1.00 1.13 (0.94–1.37) 1.64 (1.27–2.13) ***
1.00 1.25 (1.02–1.52)*** 1.72 (1.31–2.25)***
1.00 1.18 (0.96–1.44) 1.58 (1.20–2.09)**
1.00 1.05 (0.84–1.29) 1.79 (1.40–2.30)***
1.00 1.20 (0.81–1.27) 1.61 (1.24–2.09)***
1.00 0.97 (0.77–1.20) 1.50(1.15–1.96)**
1.00 1.23 (1.03–1.48) * 1.64 (1.16–2.32)***
1.00 1.10 (0.91–1.33) 1.33 (0.93–1.92)
1.00 1.05 (0.73–1.27) 1.22 (0.85–1.77)
1.00 1.73 (1.11–2.67)**
1.00e,f,g 1.23 (0.84–2.11)
1.00 1.19 (0.75–1.91)
1.00 1.24 (0.93–1.66)
1.00 1.16 (0.86–1.56)
1.00 1.09 (0.80–1.48)
*P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001. a Reference value = not exposed or exposed very little of the work day. b Adjusted for sex, age, and long-term sick leave in 2009. c +Education, cohabitation, children at home, occupation, chronic health complaints, disabled/injured, smoking, work-related psychosocial exposures yielding a 10% change of OR. d +Perceived mechanical workload. e Job control. f Possibilities for development. g Supportive leadership. CI, confidence interval; LTSL, long-term sick leave; OR, odds ratio.
0.93 to 1.83) (P = 0.11). The intercorrelations between the significant predictors were ranging from the Pearson r = 0.05 to 0.18. The population risk of LTSL attributable to the work-related psychosocial factors is shown in Table 4. The estimated population risk attributable to the significant estimates in the fully adjusted model was 15.2%.
DISCUSSION In a randomly drawn large cohort from the general working population in Norway, the importance of psychosocial factors at work as risk factors for LTSL was estimated over a 1-year period. The
risk for LTSL was higher in women, older workers, employees with fewer years of education, regular smokers, employees with previous LTSL, those with chronic health complaints, and disabled/injured individuals. In the fully adjusted model, self-reported exposure to high levels of role conflict, emotional demands, and low supportive leadership were significant predictors for LTSL. We estimated that about 15% of the cases with LTSL in 2010 were attributable to these three psychosocial factors at work, and a significant linear relationship with LTSL was observed for each of these risk factors. In general, it is well documented that psychosocial risk factors have an effect on both somatic and mental health problems,25,26
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TABLE 4. Calculated Population Attributable Risk (PAR %) Based on the Statistically Significant OR’s from Model 1, Model 2, and Model 3 in Table 3 Risk Factors High role conflict High emotional demands Low supportive leadership High job strain Low job control Poor or very poor possibilities for development Bullying Sum
Model 1 PAR (95% CI)
Model 2 PAR (95% CI)
Model 3 PAR (95% CI)
5.80 (2.12–9.85) 6.65 (1.11–11.94) 7.31 (3.38–11.55) 7.86 (13.49–2.41) 7.67 (1.21–14,2) 3.15 (0.54–6.17) 1.91 (0.12–4.16)
6.72 (3.03–10.73) 6.85 (1.03–12.88) 6.28 (2.17–10.73) 7.51 (1.88–13.51)
5.48 (1.59–9.74) 5.96 (−0.11–12.20) 5.53 (1.29–10.13)
15.17
which in turn can lead to sick leave.7 In this study, role conflict, emotional demands, and supportive leadership seemed to be the most important predictors for LTSL. Recent studies from Norway have found that supportive leadership is a risk factor for musculoskeletal pain,27,28 and role conflict and emotional demands are found to predict mental distress.29 Musculoskeletal and mental health disorders account for a substantial part of doctor-certified sickness absence in Norway and often lead to LTSL.18,30 The strength of this study is the use of a large nationwide survey using random sampling linked to registered sickness absence data, with practically no loss to follow-up. Long-term sick leave as the outcome variable was followed up during the year after workrelated psychosocial exposures were measured by a survey questionnaire at baseline. The use of different sources of measures eliminates the potential for common method bias.31 Nevertheless, reporting bias because of the self-reported assessment of the exposure cannot be ruled out. Thus, few psychosocial aspects of the work environment can be measured objectively.32 Additional analyses among respondents without LTSL in 2009 yielded minor changes in the estimates compared with the full study sample, which indicates that reversed causality is not a likely explanation for the observed associations. The study had a rather high response rate and a large sample size; 39% did not respond at baseline, but when evaluating potential systematic differences between responders and nonresponders, Statistics Norway found no differences across the benchmarks of age, sex, and region.16 On the contrary, we do not know whether people with poor health were less likely to respond at baseline, which may have led to biased and attenuated estimates and thus threatened the internal validity. Nevertheless, studies have shown that some differences in participation in questionnaire surveys related to sociodemographic variables and health status do not produce biased risk estimates.33,34 Because of data protection issues, we could not obtain information regarding diagnosis for the medically confirmed sick leave. Moreover, we could not obtain data on the number of sick leave periods, the length of each period, or start and stop dates for a given period. The chosen cutoff defining LTSL (40 days or more) during a calendar year is most likely a reasonable proxy for LTSL and one that allows us to compare our findings to those of other studies of psychosocial predictors of LTSL. Role conflict and emotional demands stand out as important risk factors for LTSL in this study, and our results are in line with previous general working population studies in Denmark.9,11 Separate analyses for men and women demonstrated an association of high emotional demands and LTSL among men, but not among women, in line with the results from a Danish study.11 In addition, it is, however, possible that the scale emotional demands might have measured multiple constructs—(1) emotional demands and (2) de792
mand for hiding emotions. When separating the items, demands for hiding emotions were found to be the strongest predictor for LTSL. Previous studies have indicated that the working environments in Denmark and Norway have many similarities,35 although there are some minor differences in workers’ sick leave compensation between the countries.36 This study further supports that role conflict and emotional demands stand out as important risk factors for LTSL in the general working population, but more population studies in other countries measuring these factors are needed to determine whether the findings apply elsewhere. A low level of supportive leadership was an important factor in this study and demonstrated a linear relationship with LTSL. Our finding is in line with other cohort studies from Norway,18,30 whereas a recent population study of the Danish workforce found no association between social support from supervisors or quality of leadership and LTSL.9 We investigated the importance of the core dimensions of the job demand–control model as risk factors for LTSL and, as with other prospective and general working population studies, we found that high job demand was not a significant predictor.13,37 By contrast, the finding that low control was not associated with LTSL is contradictory to previous research.2,8,37,38 Nevertheless, job control almost reached significance in model 2, and the point estimate was similar to previous prospective studies.5,13 Moreover, job strain (ie, high job demands and low job control) was significantly associated with LTSL in model 2 but was no longer significant when adjusted for work-related mechanical exposures. The results were less consistent for the other psychosocial factors assessed in this study. Bullying was not a significant predictor for LTSL when adjusted for supportive leadership, low possibilities for development, and low job control. Nevertheless, our item might measure a milder form for bullying, and we cannot rule out the possibility that items measuring more serious acts of bullying at work39 would have been stronger associated with LTSL in this study. Nevertheless, previous studies have found rather weak associations between bullying and sick leave,40 and to our knowledge bullying as a risk factor for LTSL has not been studied in a general working population. The possibility for development was not a significant predictor of LTSL in the fully adjusted model. Few prospective studies have measured the possibilities for development and registry-based sick leave, and the results are somewhat inconsistent.6,11 In line with Lund et al11 and Roelen et al,41 we found no association between job insecurity and LTSL. The PAR estimate of 15% underlines the importance of work-related psychosocial exposures as risk factors for LTSL. Few studies have estimated the population at risk attributable to psychosocial factors, and it is important to consider that the accuracy of the population-attributable risk (%) depends on the completeness of the specified model, the categorization of the exposure variables,
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JOEM r Volume 56, Number 8, August 2014
and the level of exposure in a given population. Nevertheless, similar results were found in a study of individuals in mainly low-skilled jobs after adjustment for socioeconomic class.15 Although the studies are not wholly comparable, the findings are interesting and reveal the importance of taking psychosocial factors into account in measures for prevention of absence.
CONCLUSIONS This study revealed a substantial relationship between selfreported low supportive leadership, high emotional demands, role conflict, and subsequent LTSL in the working population. Interventions aimed at reducing LTSL in the general working population may benefit from focusing on emotionally demanding work, supportive leadership, and role conflict.
REFERENCES 1. OECD. Sickness, Disability and Work: Breaking the Barriers. OECD Publishing; 2010. 2. Laaksonen M, Pitkaniemi J, Rahkonen O, Lahelma E. Work arrangements, physical working conditions, and psychosocial working conditions as risk factors for sickness absence: Bayesian analysis of prospective data. Ann Epidemiol. 2010;20:332–338. 3. Luz J, Green MS. Sickness absenteeism from work—a critical review of the literature. Public Health Rev. 1997;25:89–122. 4. Allebeck P, Mastekaasa A. Swedish council on technology assessment in health care (SBU). Chapter 5. Risk factors for sick leave—general studies. Scand J Public Health Suppl. 2004;63:49–108. 5. Duijts SF, Kant I, Swaen GM, van den Brandt PA, Zeegers MP. A metaanalysis of observational studies identifies predictors of sickness absence. J Clin Epidemiol. 2007;60:1105–1115. 6. Christensen KB, Nielsen ML, Rugulies R, Smith-Hansen L, Kristensen TS. Workplace levels of psychosocial factors as prospective predictors of registered sickness absence. J Occup Environ Med. 2005;47:933–940. 7. Karasek R, Theorell T. Healthy Work: Stress, Productivity, and the Reconstruction of Working Life. New York: Basic Books; 1990. 8. Head J, Kivim¨aki M, Martikainen P, Vahtera J, Ferrie JE, Marmot MG. Influence of change in psychosocial work characteristics on sickness absence: the Whitehall II study. J Epidemiol Community Health. 2006;60: 55–61. 9. Rugulies R, Aust B, Pejtersen JH. Do psychosocial work environment factors measured with scales from the Copenhagen Psychosocial Questionnaire predict register-based sickness absence of 3 weeks or more in Denmark? Scand J Public Health. 2010;38:42–50. 10. Clausen T, Nielsen K, Carneiro GI, Borg V. Job demands, job resources and long-term sickness absence in the Danish eldercare services: a prospective analysis of register-based outcomes. J Adv Nurs. 2011;68:127–136. 11. Lund T, Labriola M, Christensen KB, B¨ultmann U, Villadsen E, Burr H. Psychosocial work environment exposures as risk factors for long-term sickness absence among Danish employees: results from DWECS/DREAM. J Occup Environ Med. 2005;47:1141–1147. 12. Voss M, Floderus B, Diderichsen F. Physical, psychosocial, and organisational factors relative to sickness absence: a study based on Sweden Post. Occup Environ Med. 2001;58:178–184. 13. Labriola M, Lund T, Burr H. Prospective study of physical and psychosocial risk factors for sickness absence. Occup Med (Oxford). 2006;56:469–474. 14. Bang Christensen K, Lund T, Labriola M, Villadsen E, B¨ultmann U. The fraction of long-term sickness absence attributable to work environmental factors: prospective results from the Danish Work Environment Cohort Study. Occup Environ Med. 2007;64:487–489. 15. Nielsen ML, Rugulies R, Smith-Hansen L, Christensen KB, Kristensen TS. Psychosocial work environment and registered absence from work: estimating the etiologic fraction. Am J Ind Med. 2006;49:187–196. 16. Statistics Norway. Samordnet levek˚arsundersøkelse 2009—Tverrsnitt. Tema: Arbeidsmiljø. Report in Norwegian. Oslo: Statistics Norway; 2010. 17. Lund T, Labriola M, Christensen KB, B¨ultmann U, Villadsen E. Physical work environment risk factors for long term sickness absence: prospective findings among a cohort of 5357 employees in Denmark. BMJ 2006;332:449– 452. 18. Foss L, Gravseth HM, Kristensen P, et al. The impact of workplace risk factors on long-term musculoskeletal sickness absence: a registry-based 5-year
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Work-Related Psychosocial Risk Factors for Long-Term Sick Leave A Prospective Study of the General Working Population in Norway Cecilie Aagestad, MSc, H˚akon A. Johannessen, PhD, Tore Tynes, MD, PhD, Hans Magne Gravseth, MD, PhD, and Tom Sterud, PhD Objective: To examine the effect of work-related psychosocial exposures on long-term sick leave (LTSL) in the general working population. Methods: A prospective study of the general working population in Norway. Eligible respondents were interviewed in 2009 and registered with at least 100 working days in 2009 and 2010 (n = 6758). The outcome was medically confirmed LTSL of 40 days or more during 2010. Results: In the fully adjusted model, high exposure to role conflict (odds ratio [OR], 1.58; 95% confidence interval [CI], 1.20 to 2.09), emotional demands (OR, 1.32; 95% CI, 1.03 to 1.69), and low supportive leadership (OR = 1.50; 95% CI, 1.15 to 1.96) predicted LTSL. A test for trend was statistically significant for all factors (P ≤ 0.05). We estimated that 15% of LTSL cases were attributable to these factors. Conclusions: This study underlines the importance of taking into account psychosocial exposures as risk factors for LTSL.
S
ick leave generates considerable public financial costs to society, and expenditures are high in the Nordic countries and highest in Norway.1 Several studies have found that stressful characteristics at work predict sick leave2–5 ; however, uncertainty persists about which factors in the psychosocial work environment have the greatest effect on sick leave. Identifying these factors may help prevent individual ill-health and reduce economic costs for society. The main focus in most previous studies has been the importance of the job demand–control (social support) model as a predictor for sick leave.4,6 The job strain model suggests that high job demands will have the greatest adverse effect on health in those with low job control.7,8 In a 2004 systematic review, low job control seemed to be the best documented risk factor for increased sickness absence.4 The effect of high demand, social support, and the combination of high job demands and low control (job strain) was not conclusive, though, and few studies had addressed other workrelated psychosocial factors.4 In more recent studies taking a wider range of psychosocial factors into account, “new” factors like emotional demands, role conflict, and quality of leadership emerged as potentially important for long-term sick leave (LTSL).9,10 Overall, however, the evidence for most work-related psychosocial factors remains limited or inconclusive. Assessment of the relationships between work-related psychosocial factors and LTSL thus remains a topic of interest. Few studies have taken multiple psychosocial factors into account when From the Department of Occupational Health Surveillance (Ms Aagestad and Drs Johannessen, Tynes, Gravseth, and Sterud), National Institute of Occupational Health, Oslo; and Department of Behavioral Sciences (Ms Aagestad), Institute of Basic Medical Sciences, Faculty of Medicine, University of Oslo, Norway. Authors Aagestad, Johannessen, Tynes, Gravseth, and Sterud have no relationships/conditions/circumstances that present potential conlict of interest. The JOEM editorial board and planners have no financial interest related to this research. Address correspondence to: Cecilie Aagestad, MSc, Department of Occupational Health Surveillance, National Institute of Occupational Health, PO Box 8149 Dep, NO-0033 Oslo, Norway ([email protected]). C 2014 by American College of Occupational and Environmental Copyright Medicine DOI: 10.1097/JOM.0000000000000212
Learning Objectives
r Summarize the new findings on work-related psychosocial r r
exposures associated with the risk of long-term sick leave in Norwegian workers. Identify the estimated fractions of long-term sick leave cases attributable to psychosocial factors. Discuss the potential implications for interventions to reduce long-term sick leave in the general population.
studying LTSL, and few have considered the potential confounding of mechanical factors.2,11–13 In addition, most recent national-level studies on medically confirmed LTSL and psychosocial risk factors have been conducted in Denmark, and these findings remain to be confirmed in other nationally representative population studies. By combining data on prevalence and risk, this study enables us to estimate the proportion of LTSL cases in the population attributable to psychosocial exposures at work. Only a few former studies have provided such information.14,15 The aim of this article was, therefore, to identify the psychosocial factors with the greatest effect on LTSL. We tested the effect of a wide range of work-related psychosocial factors in a randomly selected prospective cohort from the general working-age population in Norway. Potential confounders such as age, sex, cohabitation, children living at home, education, occupation, previous high level of sick leave, chronic health condition, disability, smoking, and mechanical working conditions were taken into account.
STUDY POPULATION AND METHODS Data were provided from the nationwide survey of living conditions/work environment, conducted by Statistics Norway. Data were collected during the period June 22, 2009, to January 9, 2010, by personal telephone interviews (0.5% of completed interviews were face to face). Prior to telephone contact, potential respondents were informed by mail about the study, the topic of the study, and data/privacy protection.
Population Eligible respondents were community-living Norwegian residents aged 18 to 69 years. In 2009, a gross sample of 20,136 was randomly drawn from this population. Of these, a total of 12,255 persons were interviewed (60.9%). The baseline sample was compared with the gross sample according to the benchmarks of age, sex, and region, and no major differences were detected (Table 1).16 Data on sick leave were obtained by a merger between the survey of living conditions/work environment and the national registry of social transfer payments. The registry includes all economically active individuals aged 16 to 69 years in Norway (ie, those with a minimum of 4 hours per average working week) in the reference period. Respondents who were in paid work for at least 1 hour during the reference week or temporarily absent from such work and had
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TABLE 1. Gross Sample, Baseline Sample and the Difference in Percentage Points Between Baseline and Gross Sample According to Sex, Age, and Region (Percentage)
N Sex Male Female Age, yrs 16–24 25–44 45–66 ≥67 Region Akershus and Oslo Hedmark and Oppland Rest of Southeast Norway Agder and Rogaland Western Norway Mid Norway North Norway
Gross Sample
Baseline Sample
Dropouts
20,136
12,255
7,881
51.7 48.3
50.2 49.8
51.4 45.9
− 1.5 1.5
13.3 41.2 42.2 3.3
13.0 38.5 44.9 3.7
13.9 45.3 38.1 2.7
− 0.3 − 2.7 2.7 0.4
24 7.7 18.6 14.4 16.8 9.2 9.4
23.4 7.8 18.1 14.6 17.1 9.6 9.3
24.7 7.4 19.5 14.1 16.4 8.5 9.5
− 0.6 0.1 − 0.5 0.2 0.3 0.4 − 0.1
worked for at least 100 actual working days during a year both in 2009 and 2010 constituted the follow-up sample in this article (n = 6758).
Sick Leave Long-term sick leave was defined as medically confirmed sick leave for a period of 40 or more actual working days (ie, 8 weeks or more) during 2010, the year after the initial survey was undertaken. A similar definition of LTSL has been applied in other studies.14,17,18
Risk Factors Psychosocial risk factors were measured with six scales and two single items. A Cronbach α was estimated for each included scale. Quantitative demands at work was measured with the following two items from The General Nordic Questionnaire for Psychological and Social Factors at Work (QPS)19 (α = 0.70): (1) “How often is it necessary to work at a rapid pace?” and (2) “How often do you have too much to do?” Answer categories were “very seldom or never,” “rather seldom,” “sometimes,” “rather often,” and “very often or always.” Role conflict was measured with the following three items from QPS19 (α = 0.64): (1) “How often do you receive incompatible requests from two or more people?”; (2) “How often are you given assignments without adequate resources to complete them?”; and (3) “How often do you have to do things that you feel should be done differently?” Answer categories were “very seldom or never,” “rather seldom,” “sometimes,” “rather often,” and “very often or always.” Supportive leadership was measured with the following three items from QPS19 (α = 0.70): (1) “If needed, how often can you get support and help from your immediate superior with your work?”; (2) “ Are your work achievements appreciated by your immediate superior?”; and (3) “Does your immediate superior treat employees fairly and equally?” Answer categories were “very seldom or never,” “rather seldom,” “sometimes,” “rather often,” and “very often or always.” Job control was measured with two questions from QPS19 and two questions developed by Statistics Norway16 (α = 0.71) as follows: (1) “To what extent can you set your own work pace”; (2) “To what extent can you influence decisions that are important for your work?”; (3) “To what extent are you free to decide how to go about your work?”; and (4) “To what extent are you free to decide 788
Difference
your own tasks?” Answer categories were “to a very great extent,” “to a great extent,” “to some extent,” “not really,” and “hardly at all.” For these work-related psychosocial factors, the five-point scale score was converted into the following three categories: low (1.0 to 2.0), medium (2.1 to 3.0), and high (3.1 to 5.0). By dichotomizing job control (low = 1, medium and high = 0) and quantitative demands (high = 1, medium and low = 0), we constructed a job strain variable—low strain (job control = 0, quantitative demands = 0); passive (job control = 1, quantitative demands = 0); active (job control = 0, quantitative demands = 1); and high strain (job control = 1, quantitative demands = 1). Low strain was set as the reference value. Emotional demands was measured with the following two items developed by Statistics Norway16 (α = 0.69): (1) “In your work, to what extent do you need to deal with strong feelings such as sorrow, anger, desperation, frustration, and so on from customers, clients, or other people who are not employed at your workplace?” Answer categories were “to a very great extent, “to a great extent,” “to some extent,” “not really,” and “not at all”; and (2) “In your work, to what extent do you need to conceal negative feelings such as anger, irritation, frustration, and so on for customers, clients, or other people who are not employed at your workplace?” Answer categories were “to a great extent,” “to some extent,” “not really,” and “not at all.” For these work-related psychosocial factors, the mean scale score was converted into the following three categories: low (1.0 to 2.0), medium (2.1 to 3.0), and high (3.1 to 5.0). All variables were coded so that high exposures indicate assumed negative exposure such as high quantitative demands, high role conflict, high emotional demands, high job strain, low job control, and low supportive leadership. Possibilities for development (reversed) was measured with the following two items developed by Statistics Norway16 (α = 0.72): “In your job, how good are your opportunities to” (1) “develop your skills in the areas that interest you”; and (2) “make use of the skills, knowledge, and experience that you have gained through your education and past work?” Answer categories were “very good,” “good,” “poor,” and “very poor.” The last two categories were combined and used as one category, “poor or very poor.” Bullying was measured with the following two items developed by Statistics Norway: “Do you yourself sometimes get bothered or teased in an unpleasant way by your colleagues?” and “Do you yourself sometimes get bothered
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JOEM r Volume 56, Number 8, August 2014
or teased in an unpleasant way by superiors?” Answer categories were “yes, once or more a week,” “yes, once or more a month,” and “no.” The question and answer categories were computed into one dichotomous variable (yes = 1, no = 0). Job insecurity was measured with the following one item developed by Statistics Norway16 : “Do you believe that you are at risk of losing your job due to your company’s closing, downsizing, or other reasons over the coming 3 years?” Answer categories were “yes, due to its closing,” “yes, due to downsizing,” “yes, for other reasons,” and “no.” The categories were recoded into one dichotomous variable (yes = 1, no = 0). Potential confounders such as sex, age, and educational level were based on administrative registry data. Education was coded into five educational levels. Married/registered partner/cohabiting was coded as yes = 1, no = 0, as was children in the household. Occupation was based on an open questionnaire and coded by Statistics Norway into a professional title in accordance with the International Standard Classification of Occupations–88 and recoded into 10 occupational groups based on one-digit codes. Chronic health problem was measured with a single item as follows: “Do you have any long-term illnesses or health problems? This includes any illnesses or problems that are seasonal, or that are intermittent. The prerequisite is that the condition must have lasted, or be expected to last, at least 6 months.” Disability was measured with a single item as follows: “Are you disabled, or do you suffer pain as a result of an injury? This includes pains that are intermittent.” Smoking was measured with the following two items: “Do you sometimes smoke?” “Yes” respondents were asked, “Do you smoke every day or occasionally?” These variables were recoded into regular smokers versus non- or sometimes-smokers. Perceived mechanical workload was measured with the following seven items: neck flexion, hands above shoulders, hand/arm repetition, squatting/kneeling, standing, work with upper body bent forward, and awkward lifting, which have been shown to predict LTSL and are described in greater detail elsewhere.20 Scores were coded on a scale from 1 (not exposed or exposed very little of the work day) to 4 (exposed three fourths of the work day or more).
Statistics The associations between work environment and LTSL were calculated by logistic regression analyses as odds ratios (ORs) with 95% confidence intervals (CIs) with adjustment for potential confounders. In this study, medically confirmed sick leave days are registered for 1 year after the collection of survey data, and we have no information about the exact day of the interview or start and stop date for each sick leave episode. It was, therefore, not possible to conduct time-to-event analyses. On the contrary, it has been shown that if the follow-up period is short and the outcome is generally rare (when the probability of the event not occurring is close to 1), the regression coefficients of the logistic model approximate those of the proportional hazards model.21 Three models were evaluated. In model 1, we adjusted for sex, age, and registered LTSL in 2009. In model 2, further adjustments were made for educational level, cohabitation, children living at home, occupation, chronic health complaints, disabled/injured, and smoking. In model 3, further adjustments were made for work-related mechanical exposures. To limit the potential for overadjustment, each work-related psychosocial predictor was adjusted only for other work-related psychosocial predictors that were first estimated to exert an influence more than a certain threshold level. This estimation was made a priori, on the basis of the following procedure suggested by Rothman et al22 and applied to baseline data. In the first step, crude OR was separately estimated for each work-related factor. In the second step, each of the other work-related variables was entered one at a time. If the inclusion of a potential confounder resulted in a change in the OR of 10% or more, that variable was treated as a real confounder in the multiple regression models. We did additional separate analyses
Work-Related Psychosocial Risk Factors for Long-Term Sick Leave
for men and women in the fully adjusted model. Finally, to evaluate changes in the estimates, we did additional analyses among respondents with no LTSL registered in 2009. All statistical analyses were conducted with PASW Statistics package (formerly SPSS), version 20.0 (IBM, Armonk, NY). For statistically significant work-related factors in the regression analyses in the three models, we calculated the population attributable risk (PAR) estimates with 95% CI. In contrast to OR estimates, the PAR estimate combines data on prevalence and a measure of association to provide a quantitative estimate of the proportion of cases in the population that is attributable to a particular exposure. The method is described in detail by Natarajan et al.23 On the basis of the assumption that the predictors are statistically independent and no interaction exists between the effects of predictors on the outcome, the summary attributable risk in model 3 was calculated according to a mathematical formula described by Miettinen.24
RESULTS During the follow-up period, 635 (9.4%) were classified with LTSL. Table 2 describes the distribution of sociodemographic variables and health variables at baseline and the associated risk of LTSL at follow-up. The risk was significantly higher among women than among men (12.1% vs 7.2%, respectively), older workers (11.2% in the 55 to 69 years age group vs 8% to 9% in the other age groups), and those with lower education (13.9% for basic school level vs 3.8% for 4 years or older of university/college). A higher risk was also seen among those in elementary occupations (19.5% vs 4.9% for professionals), persons with a chronic health complaint (18.9% vs 6.7%), those who were disabled/injured (20% vs 8.3%), regular smokers (12.9% vs 8.6%), and those having LTSL during the baseline year (36.1% vs 6.9%). Civil status and children in the household were not related to LTSL. Table 3 shows the results of multiple logistic regression analyses with baseline psychosocial risk factors as the predictors and LTSL during the follow-up period as the outcome. In model 1 (adjusting for sick leave during the baseline year, age, and sex), significant associations with LTSL were found for high role conflict, high emotional demands, low supportive leadership, high job strain, low possibilities for development, low job control, and those reporting bullying. In model 2, low job control was close to significant. The main confounder was occupation. Possibilities for development were no longer a significant predictor when adjusted for occupation and education. Bullying was no longer a significant predictor when adjusted for work-related psychosocial confounders. In the fully adjusted model 3, significant predictors were high role conflict (OR, 1.58; 95% CI, 1.20 to 2.09), high emotional demands (OR, 1.32; 95% CI, 1.03 to 1.69), and low supportive leadership (OR, 1.50; 95% CI, 1.15 to 1.96). Job strain was close to significant. A test for linear trend was statistically significant for all three predictors in the model—role conflict (OR, 1.17; 95% CI, 1.05 to 1.30), emotional demands (OR, 1.37; 95% CI, 1.03 to 1.25), and supportive leadership (OR, 1.12; 95% CI, 1.02 to 1.23). In further analyses, we evaluated the effect of the single items included in each of these significant predictors separately. The estimates were rather consistent at singleitem level. Nevertheless, different estimates were observed for the two items constituting emotional demands (1) (OR, 1.16; 95% CI, 0.91 to 1.48) and (2) (OR, 1.49; 95% CI, 1.17 to 1.90). When we separately evaluated the risk for LTSL among men and women, most differences were small and not significant (P > 0.05). The largest difference detected was in high emotional demands for women (OR, 0.97; 95% CI, 0.71 to 1.33) and men (OR, 2.07; 95% CI, 1.36 to 3.16), (P ≤ 0.05). Moreover, when excluding respondents with LTSL in 2009 from the analyses, minor changes in the estimates were detected, with predictors being low supportive leadership (OR, 1.41; 95% CI, 1.03 to 1.92), high emotional demands (OR, 1.35; 95% CI, 1.01 to 1.80), and high role conflict (OR, 1.31; 95% CI,
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TABLE 2. Distribution of the Sociodemographic Variables and Health Variables at Baseline and the Associated Risk of LTSL During the Follow-Up Period
Total Age, yrs 17–24 25–34 35–44 45–54 55–69 Sex Male Female Education level Basic school level Upper secondary education, not finished Upper secondary education University/college 4 yrs University/college 4 yrs+ Missing Cohabitation Living alone Living with a partner Missing Children at home No Yes Missing Occupation Legislators, senior officials, and manager Professionals Technicians and associate professionals Clerks Service workers and shop and market sales workers Skilled agricultural and fishery workers Craft and related trades workers Plant and machine operators and assemblers Elementary occupations Other occupations Missing Chronic health complaints No Yes Missing Disabled/injured No Yes Missing Smoking No Yes Missing Long-term sick leave in 2009 No Yes
N
Cases (n*)
Cases, % (95% CI)
6,758
635
9.4 (8.70–10.10)
370 1,239 1,920 1,859 1,370
31 113 171 167 153
8.4 (5.57–11.23) 9.1 (7.50–10.70) 8.9 (7.63–10.17) 9.0 (7.70–10.30) 11.2 (9.53–12.87)
3,688 3,070
264 371
7.2 (6.37–8.03) 12.1 (10.95–13.25)
855 653 2,183 2,147 786 134
119 81 241 157 30
13.9 (11.30–15.90) 12.4 (9.87–14.93) 11.0 (9.69–12.31) 7.3 (6.20–8.40) 3.8 (2.46–5.14)
1,454 4,667 2
154 481
9.6 (8.14–11.02) 9.3 (8.55–10.14)
3,132 3,626 2
299 336
9.5 (8.52–10.58) 9.3 (8.32–10.21)
789 1,093 2,011 484 1,040 33 667 388 128 114 11
57 53 169 49 156 2 67 43 25 14
7.2 (5.40–9.00) 4.9 (3.62–6.18) 8.4 (7.19–9.61) 10.1 (7.42–12.78) 15.0 (12.83–17.17) 6.1 (−2.07–14.27) 10.0 (7.72–12.28) 11.1 (7.97–14.23) 19.5 (12.64–26.36) 12.3 (6.27–18.33)
5,232 1,504 22
348 284
6.7 (6.02–7.38) 18.9 (16.92–20.88)
5,595 508 22
504 127
8.3 (7.57–8.95) 20.0 (16.88–23.12)
5,482 1,252 24
470 162
8.6 (7.86–9.34) 12.9 (11.04–14.76)
6,182 576
427 208
6.9 (6.27–7.53) 36.1 (32.18–40.02)
*Long-term sick leave of 40 days or more during the follow-up.
790
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Work-Related Psychosocial Risk Factors for Long-Term Sick Leave
TABLE 3. Multiple Logistic Regression: LTSL During Follow-Up Regressed on Psychosocial Risk Factors Measured at Baselinea
Quantitative demands Low Medium High Job control High Medium Low Job strain Low strain Passive Active High strain Emotional demands Low Medium High Role conflict Low Medium High Supportive leadership High Medium Low Possibilities for development Very good Good Poor or very poor Bullying No Yes Job insecurity No Yes
N
Cases, n (%)
6,745 537 1,713 4,495 6,687 2,063 3,249 1,375 6,682 1,808 410 3,499 965 6,745 3,548 2,017 1,180 6,745 3,934 2,119 692 6,578 4,421 1,506 651 6,751 3,118 3,283 350 6,700 6,517 183 6,673 6,118 555
632 (9.4) 49 (9.1) 143 (8.3) 440 (9.8) 629 (9.4) 165 (8) 289 (8.9) 175 (12.7) 628 (9.4) 156 (8.6) 34 (8.3) 297 (8.5) 141 (14.6) 633 (9.4) 284 (8) 194 (9.6) 155 (13.1) 633 (9.4) 334 (8.5) 205 (9.7) 94 (13.6) 617 (9.4) 376 (8.5) 141 (9.4) 102 (15.7) 634 (9.4) 247 (7.9) 336 (10.2) 51 (14.6) 630 (9.4) 601 (9.2) 29 (15.8) 623 (9.3) 560 (9.2) 63 (11.4)
Model 1 OR (95% CI)b
Model 2 OR (95% CI)c
Model 3 OR (95%CI)d
1.00 0.95 (0.66–1.35) 1.10 (0.79–1.53)
1.00 0.99 (0.68–1.42) 1.21 (0.86–1.69)
1.00 0.94 (0.65–1.36) 1.06 (0.75–1.49)
1.00 1.05 (0.86–1.29) 1.36 (1.07–1.73) **
1.00 1.04 (0.83–1.29) 1.28 (0.99–1.65)
1.00 1.02 (0.81–1.27) 1.18 (0.91–1.52)
1.00 0.79 (0.53–1.19) 0.97 (0.78–1.20) 1.53 (1.18–1.99) *
1.00 0.78 (0.51–1.19) 1.04 (0.84–1.30) 1.50 (1.15–1.95)*
1.00 0.74 (0.49–1.14) 0.96 (O.77–1.20) 1.30 (0.99–1.71)
1.00 1.07 (0.87–1.31) 1.37 (1.20–1.72) **
1.00 1.08 (0.87–1.34) 1.39 (1.09–1.77) **
1.00 1.09 (0.88–1.35) 1.32 (1.03–1.69)*
1.00 1.13 (0.94–1.37) 1.64 (1.27–2.13) ***
1.00 1.25 (1.02–1.52)*** 1.72 (1.31–2.25)***
1.00 1.18 (0.96–1.44) 1.58 (1.20–2.09)**
1.00 1.05 (0.84–1.29) 1.79 (1.40–2.30)***
1.00 1.20 (0.81–1.27) 1.61 (1.24–2.09)***
1.00 0.97 (0.77–1.20) 1.50(1.15–1.96)**
1.00 1.23 (1.03–1.48) * 1.64 (1.16–2.32)***
1.00 1.10 (0.91–1.33) 1.33 (0.93–1.92)
1.00 1.05 (0.73–1.27) 1.22 (0.85–1.77)
1.00 1.73 (1.11–2.67)**
1.00e,f,g 1.23 (0.84–2.11)
1.00 1.19 (0.75–1.91)
1.00 1.24 (0.93–1.66)
1.00 1.16 (0.86–1.56)
1.00 1.09 (0.80–1.48)
*P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001. a Reference value = not exposed or exposed very little of the work day. b Adjusted for sex, age, and long-term sick leave in 2009. c +Education, cohabitation, children at home, occupation, chronic health complaints, disabled/injured, smoking, work-related psychosocial exposures yielding a 10% change of OR. d +Perceived mechanical workload. e Job control. f Possibilities for development. g Supportive leadership. CI, confidence interval; LTSL, long-term sick leave; OR, odds ratio.
0.93 to 1.83) (P = 0.11). The intercorrelations between the significant predictors were ranging from the Pearson r = 0.05 to 0.18. The population risk of LTSL attributable to the work-related psychosocial factors is shown in Table 4. The estimated population risk attributable to the significant estimates in the fully adjusted model was 15.2%.
DISCUSSION In a randomly drawn large cohort from the general working population in Norway, the importance of psychosocial factors at work as risk factors for LTSL was estimated over a 1-year period. The
risk for LTSL was higher in women, older workers, employees with fewer years of education, regular smokers, employees with previous LTSL, those with chronic health complaints, and disabled/injured individuals. In the fully adjusted model, self-reported exposure to high levels of role conflict, emotional demands, and low supportive leadership were significant predictors for LTSL. We estimated that about 15% of the cases with LTSL in 2010 were attributable to these three psychosocial factors at work, and a significant linear relationship with LTSL was observed for each of these risk factors. In general, it is well documented that psychosocial risk factors have an effect on both somatic and mental health problems,25,26
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TABLE 4. Calculated Population Attributable Risk (PAR %) Based on the Statistically Significant OR’s from Model 1, Model 2, and Model 3 in Table 3 Risk Factors High role conflict High emotional demands Low supportive leadership High job strain Low job control Poor or very poor possibilities for development Bullying Sum
Model 1 PAR (95% CI)
Model 2 PAR (95% CI)
Model 3 PAR (95% CI)
5.80 (2.12–9.85) 6.65 (1.11–11.94) 7.31 (3.38–11.55) 7.86 (13.49–2.41) 7.67 (1.21–14,2) 3.15 (0.54–6.17) 1.91 (0.12–4.16)
6.72 (3.03–10.73) 6.85 (1.03–12.88) 6.28 (2.17–10.73) 7.51 (1.88–13.51)
5.48 (1.59–9.74) 5.96 (−0.11–12.20) 5.53 (1.29–10.13)
15.17
which in turn can lead to sick leave.7 In this study, role conflict, emotional demands, and supportive leadership seemed to be the most important predictors for LTSL. Recent studies from Norway have found that supportive leadership is a risk factor for musculoskeletal pain,27,28 and role conflict and emotional demands are found to predict mental distress.29 Musculoskeletal and mental health disorders account for a substantial part of doctor-certified sickness absence in Norway and often lead to LTSL.18,30 The strength of this study is the use of a large nationwide survey using random sampling linked to registered sickness absence data, with practically no loss to follow-up. Long-term sick leave as the outcome variable was followed up during the year after workrelated psychosocial exposures were measured by a survey questionnaire at baseline. The use of different sources of measures eliminates the potential for common method bias.31 Nevertheless, reporting bias because of the self-reported assessment of the exposure cannot be ruled out. Thus, few psychosocial aspects of the work environment can be measured objectively.32 Additional analyses among respondents without LTSL in 2009 yielded minor changes in the estimates compared with the full study sample, which indicates that reversed causality is not a likely explanation for the observed associations. The study had a rather high response rate and a large sample size; 39% did not respond at baseline, but when evaluating potential systematic differences between responders and nonresponders, Statistics Norway found no differences across the benchmarks of age, sex, and region.16 On the contrary, we do not know whether people with poor health were less likely to respond at baseline, which may have led to biased and attenuated estimates and thus threatened the internal validity. Nevertheless, studies have shown that some differences in participation in questionnaire surveys related to sociodemographic variables and health status do not produce biased risk estimates.33,34 Because of data protection issues, we could not obtain information regarding diagnosis for the medically confirmed sick leave. Moreover, we could not obtain data on the number of sick leave periods, the length of each period, or start and stop dates for a given period. The chosen cutoff defining LTSL (40 days or more) during a calendar year is most likely a reasonable proxy for LTSL and one that allows us to compare our findings to those of other studies of psychosocial predictors of LTSL. Role conflict and emotional demands stand out as important risk factors for LTSL in this study, and our results are in line with previous general working population studies in Denmark.9,11 Separate analyses for men and women demonstrated an association of high emotional demands and LTSL among men, but not among women, in line with the results from a Danish study.11 In addition, it is, however, possible that the scale emotional demands might have measured multiple constructs—(1) emotional demands and (2) de792
mand for hiding emotions. When separating the items, demands for hiding emotions were found to be the strongest predictor for LTSL. Previous studies have indicated that the working environments in Denmark and Norway have many similarities,35 although there are some minor differences in workers’ sick leave compensation between the countries.36 This study further supports that role conflict and emotional demands stand out as important risk factors for LTSL in the general working population, but more population studies in other countries measuring these factors are needed to determine whether the findings apply elsewhere. A low level of supportive leadership was an important factor in this study and demonstrated a linear relationship with LTSL. Our finding is in line with other cohort studies from Norway,18,30 whereas a recent population study of the Danish workforce found no association between social support from supervisors or quality of leadership and LTSL.9 We investigated the importance of the core dimensions of the job demand–control model as risk factors for LTSL and, as with other prospective and general working population studies, we found that high job demand was not a significant predictor.13,37 By contrast, the finding that low control was not associated with LTSL is contradictory to previous research.2,8,37,38 Nevertheless, job control almost reached significance in model 2, and the point estimate was similar to previous prospective studies.5,13 Moreover, job strain (ie, high job demands and low job control) was significantly associated with LTSL in model 2 but was no longer significant when adjusted for work-related mechanical exposures. The results were less consistent for the other psychosocial factors assessed in this study. Bullying was not a significant predictor for LTSL when adjusted for supportive leadership, low possibilities for development, and low job control. Nevertheless, our item might measure a milder form for bullying, and we cannot rule out the possibility that items measuring more serious acts of bullying at work39 would have been stronger associated with LTSL in this study. Nevertheless, previous studies have found rather weak associations between bullying and sick leave,40 and to our knowledge bullying as a risk factor for LTSL has not been studied in a general working population. The possibility for development was not a significant predictor of LTSL in the fully adjusted model. Few prospective studies have measured the possibilities for development and registry-based sick leave, and the results are somewhat inconsistent.6,11 In line with Lund et al11 and Roelen et al,41 we found no association between job insecurity and LTSL. The PAR estimate of 15% underlines the importance of work-related psychosocial exposures as risk factors for LTSL. Few studies have estimated the population at risk attributable to psychosocial factors, and it is important to consider that the accuracy of the population-attributable risk (%) depends on the completeness of the specified model, the categorization of the exposure variables,
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and the level of exposure in a given population. Nevertheless, similar results were found in a study of individuals in mainly low-skilled jobs after adjustment for socioeconomic class.15 Although the studies are not wholly comparable, the findings are interesting and reveal the importance of taking psychosocial factors into account in measures for prevention of absence.
CONCLUSIONS This study revealed a substantial relationship between selfreported low supportive leadership, high emotional demands, role conflict, and subsequent LTSL in the working population. Interventions aimed at reducing LTSL in the general working population may benefit from focusing on emotionally demanding work, supportive leadership, and role conflict.
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