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Occupational Medicine Advance Access originally published online on June 10, 2008
Occupational Medicine 2008 58(6):425-430; doi:10.1093/occmed/kqn073
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© The Author 2008. Published by Oxford University Press on behalf of the Society of Occupational Medicine. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org

Sickness absence and psychosocial work conditions: a multilevel study

Corné A. M. Roelen1,2, Sabine H. Weites3, Petra C. Koopmans2,4, Jac J. L. van der Klink2 and Johan W. Groothoff2

1 ArboNed Corporate Accounts, PO Box 158, 8000 AD Zwolle, The Netherlands
2 Department of Health Sciences, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
3 ArboNed Leeuwarden, PO Box 132, 8900 AC Leeuwarden, The Netherlands
4 ArboNed Groningen, PO Box 141, 9700 AC Groningen, The Netherlands

Correspondence to: C. A. M. Roelen, ArboNed NV, PO Box 132, 8900 AC Leeuwarden, The Netherlands. Tel: +31 58 2339233; fax: +31 58 2131823; e-mail: corne.roelen{at}arboned.nl


   Abstract
Top
 Abstract
Introduction
 Methods
 Results
 Discussion
 Conflicts of interest
 References
 
Background Psychosocial work conditions, particularly psychological job demands, are inconsistently associated with sickness absence rates. This might be the result of investigating the psychosocial work environment at the individual level, reflecting personal perceptions rather than actual demands.

Aim To investigate associations between sickness absence and psychosocial work conditions at both the individual and the workplace level.

Methods A cross-sectional study of insurance company employees (n = 395) in four departments. Psychological job demands, job control and job support were investigated at the individual level using the self-completed Questionnaire on Experience and Assessment of Work. An external occupational psychologist interviewed the supervisor and a group of employees of each department, assessing job demands, job control, job support and psychological distress at the workplace level. These data were related to the number of short (1–7 days), medium (8–21 days) and long (>21 days) episodes of sickness absence in the period January 2001 to December 2002.

Results A total of 244 questionnaires (62%) were suitable for analysis. Quantitative job control scores at the individual level differed from qualitative data at the workplace level. Self-assessed job demands and control were unrelated to sickness absence. The rates of short and long episodes of absence were higher in the department with combined high demands and low control, assessed at the workplace level.

Conclusions The associations between psychosocial work conditions and sickness absence depended on the level at which the former were assessed. More multilevel research is needed to disentangle the relations between psychosocial work conditions and sickness absence.

Keywords      Occupation; occupational psychology; psychosocial work conditions; sickness absence


   Introduction
Top
 Abstract
 Introduction
Methods
 Results
 Discussion
 Conflicts of interest
 References
 
The nature of work has changed profoundly in the last few decades. Nowadays, job characteristics rarely exceed the physical capabilities of workers and demands such as work pace, time pressure, complexity of work and conflicting tasks act as stressors. Karasek's demand–control model is the leading work stress model in occupational health psychology [1]. According to this model, job control provides resources to deal with demands. The source of strain is to be found in work that combines high demands and low control [1,2]. Many studies have tested this hypothesis, but the results do not always support it. van der Doef and Maes [3] showed that 28 of 41 studies examining the relationship between job characteristics and psychological well-being supported the strain hypothesis. De Lange et al. [4] found support for the hypothesis in eight of 19 high-quality studies. They suggested using other outcome variables, such as recorded sickness absence, to provide a more comprehensive picture of the effects of psychosocial work conditions on health.

Most studies on the associations between psychosocial work conditions and sickness absence, however, have investigated the effects of demands and control separately, reporting job control to be the strongest predictor of sickness absence [5,6]. Kondo et al. [7] investigated the association of combined high demands and low control with sickness absence. Compared to the lowest tertile of the ratio demand to control, they found the highest tertile to be significantly correlated with an increased risk of sickness absence at follow-up. High-strain jobs were also found to be associated with sickness absence and recurring spells of sick leave in the Belgian workforce [8].

The majority of studies on psychosocial work characteristics examined self-report measures [4]. The investigation of self-reported psychosocial work conditions may reflect personal perceptions rather than the actual work environment. One way to address this problem is to measure the psychosocial work environment by workplace observations [9]. Using this approach, Christensen et al. [10] reported workplace differences in the relation between sickness absence and psychosocial work characteristics, suggesting the importance of multilevel studies. The measurement of psychosocial work characteristics was demonstrated to be biased by gender, age and occupational group. Bias was much weaker or disappeared when the population was divided into principal occupational groups and analyzed in relation to the same organizational and economic characteristics [11].

We found no studies investigating psychosocial work conditions and sickness absence at different levels in the same population. Therefore, the present study investigated the association of recorded sickness absence with job demands and job control assessed at two levels in one company: the individual level and the workplace (i.e. departmental) level. The research questions were as follows:

(i) Are self-assessed psychosocial work conditions related to sickness absence?
(ii) Are independently rated workplace psychosocial work conditions related to sickness absence?

The objective of the study was to compare the results of both approaches.


   Methods
Top
 Abstract
 Introduction
 Methods
Results
 Discussion
 Conflicts of interest
 References
 
This multilevel study was designed according to Marklund et al. [12] who collected individual data by means of a survey of the employees and workplace data by interviews. We collected individual data with the Questionnaire on Experience and Assessment of Work in January 2002. This questionnaire is based on the Job Content Questionnaire and used in Dutch and Belgian research on psychosocial work characteristics [13,14]. It consists of 108 questions on work and work conditions, which were answered on a four-point Likert-type scale ranging from 1 (=always) to 4 (=never). It was developed and validated by Van Veldhoven and Meijman [15]. They measured the construct validity (H) of the subscales. Mokken reported that scales with H >0.40 were adequately unidimensional [16]. The internal consistency of the subscales was characterized by rho ({rho}), and scales with {rho} >0.80 were considered to be adequately consistent [17]. For this study, we used the following subscales: psychological job demands (11 items on workload, work pace, time pressure, conflicting demands and work accumulation; H = 0.51 and {rho} = 0.87), control over work (11 items on task discretion, task variety and decision-making authority over the content of work and its pace; H = 0.44 and {rho} = 0.90), coworker support (9 items on relationships with colleagues, appreciation, collaboration and ambience; H = 0.52 and {rho} = 0.87) and supervisor support (9 items on the relationship with the supervisor, appreciation and disputes; H = 0.58 and {rho} = 0.90). We sought ethical approval from the Medical Ethics Committee of the University Medical Center Groningen, who advised that ethical clearance was not required.

The study subjects worked in an insurance company with four departments: health insurance (A), public relations (B), finance and control (C) and indemnity insurance (D). All employees were office workers doing computer work. The employees of both insurance departments and the public relations department also had customer service tasks. Some employees of the indemnity insurance department worked as outdoor insurance agents. Departmental sickness absence levels were calculated as

Formula

Departmental sickness absence levels were highest in departments C (7%) and D (7%), whereas departments A and B had absence levels of 3 and 2%, respectively.

An external occupational health psychologist assessed the psychosocial environment of each department by interviewing the supervisor and a group of employees representing the department. The interviews gathered qualitative information about job demands, job control, job support and psychological distress as mentioned by the group, without using quantitative measures or score tables. Table 1 summarizes the outcome of these interviews. The employees working in departments A and B felt no distress; they were combined to form a reference group. The employees of department C mentioned high job demands but normal control. Employees working in department D mentioned combined high demands and low control.


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  		Table 1. Psychosocial work conditions at the workplace level

 
We recorded the first and last dates of all absences in 2001 and 2002 and calculated the number of episodes absent in this 2-year period for each employee. Short episodes (1–7 days), medium duration episodes (8–21 days) and long episodes (>21 days) of absence were considered separately. The number of absence episodes is a form of count data, for which Poisson regression model was computed using GENLOG for general log-linear analysis in SPSS for Windows version 14. In Poisson regression analysis, the dependent variable y has a distribution given the independent variables x1, x2, ... , xi:

Formula

The logarithm of the mean µ is assumed to be a linear function of the independent variables:

Formula

The Poisson distribution implies that the variance is equal to the mean (µ).

The Poisson model was a good fit for the number of medium duration absence episodes [likelihood ratio (LR) = 196; df = 221; P = 0.89] and the number of long absence episodes (LR = 151; df = 221; P = 1.00). The variance in the number of short episodes, however, was greater than the mean resulting in overdispersion. Therefore, a zero-inflated negative binomial distribution was estimated for the short episodes, using Transition Data Analysis version 6.4f. The negative binomial distribution proved to be a better fit for the number of short absence episodes. Age and gender were controlled for in both the negative binomial and the Poisson regression analysis. External factors such as marital state, number of children, household income and social support outside work were not controlled for.


   Results
Top
 Abstract
 Introduction
 Methods
 Results
Discussion
 Conflicts of interest
 References
 
Of the 395 employed subjects, 265 (67%) returned their questionnaire. Table 2 shows the participation rates in each department. The response rate in department D was relatively low [97/172 (56%)], particularly among the female employees. The age distributions in non-participants did not differ from those in the participants. The non-participants in departments A + B (reference group) had more absences in the 2-year period of study than participants, as 40 non-participants (80%) had one or more short episodes of absence compared to 72% of the participants, 16 non-participants (32%) had one or more medium episodes of absence compared to 22% of the participants and 11 non-participants (22%) had one or more long episodes of absence compared to 13% of the participants. In departments C and D, the participants tended to have more absences (Table 2).


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  		Table 2. Participants and non-participants and their sickness absence data

 
Of the returned 265 questionnaires, 21 had to be excluded because they were not complete. The questionnaires of 244 participants were eligible for statistical analysis. Table 3 shows the self-assessed psychosocial work conditions in each department. Higher scores were more unfavorable from the demand–control point of view. The employees working in department C had higher scores on job demands, which meant that they perceived higher demands than the reference group. However, the higher scores on job control meant that they experienced less control over work than the reference group. The lower scores on supervisor support meant that the personnel of department C perceived more support from their supervisor than the reference group.


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  		Table 3. Psychosocial work conditions perceived at the individual level

 
Table 4 shows the associations of sickness absence with psychosocial work conditions at the individual and the workplace level. The rates of short episodes of absence were unrelated to self-assessed work characteristics, although the rates of combined high demands and low control (demands x control) was on the verge of significance (P = 0.05) with a rate ratio (RR) of 1.1 and a 95% confidence interval (95% CI) of 1.0–1.1. The rates of short duration absence were higher in department D (RR = 1.5; 95% CI = 1.1–2.0; P < 0.01) than in the reference group. Department C had non-significant higher rates of short duration absence (RR = 1.3; 95% CI = 0.9–2.0; P = 0.23) compared to the reference group. The rate of medium duration absence was also higher in department C (RR = 1.5; 95% CI = 0.8–3.0; P = 0.18) but again not significantly higher than the rate in the reference group.


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  		Table 4. The relationship between sickness absence and psychosocial work conditions

 
Long duration absence was associated with self-assessed coworker support at the individual level. The rate of long episodes of absence was higher in department D (RR = 2.0; 95% CI = 1.0–3.9; P = 0.02) relative to the reference group.


   Discussion
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
Conflicts of interest
 References
 
The results of this multilevel study on psychosocial work conditions showed that individual employees’ perception of job control differed from control assessed at the workplace level. Moreover, self-reported job demands, control and their combination were not significantly associated with sickness absence, whereas the rates of short and long absences were higher in the department with independently assessed high demands and low control.

The strength of the present study is that it investigated psychosocial work conditions at different levels (individual and departmental) in the same population. In this way, we were able to compare the results at both levels although the individual results were quantitative data and the results at the workplace level were qualitative. The workplace interviews were performed by one occupational health psychologist, excluding interobserver bias. However, the repeatability and interobserver agreement of the interview results could not be determined.

The study had some other limitations. First, the response rate was moderate (67%) and there were some indications that sickness absence among non-participants differed from participants, which could have biased the relations between sickness absence and self-perceived psychosocial work conditions. The cross-sectional assessment of work conditions with self-report questionnaires is impeded by potential shared method variance or shared response biases, resulting in an overestimation of associations at the individual level. The results of the study were not necessarily representative of the total working population, as we restricted our research to one company.

Our study population was a sample of convenience including all employees (n = 395) working in an insurance company. They had comparable educational levels (senior secondary vocational educations in administration, bookkeeping or insurance) and income. These factors are usually regarded as a proxy for the socioeconomic status of workers. Therefore, the employees could be considered a homogeneous group with regard to their social class.

The study included employees with an above average income. Future research should clarify whether the results found in this study also apply for workers of lower socioeconomic status. Finally, coping styles and factors not related to the workplace were not controlled for. It is possible that differences in coping with work demands explained why employees in departments A and B felt less distress than those working in departments C and D. Higher absence levels in departments C and D could also point to differences in coping, as passive-avoiding coping styles are associated with sickness absence [18]. However, higher departmental absence levels could also indicate poorer health of employees.

Most studies on psychosocial work conditions have used the employee's reports of their work, which may relate as much to personal factors as to the work environment itself. Others have used some form of external assessment that may overlook the employees’ perceptions of their work environment. In the Whitehall II Study, for example, psychosocial conditions assessed by personnel managers were not highly correlated with those reported by employees [19]. Our study investigated the relationship between sickness absence and individually reported psychosocial work conditions as well as observed departmental psychosocial work conditions. The perception of psychosocial work conditions, particularly job control, at the individual level differed from the assessment at the departmental level. Self-reported psychosocial work conditions might reflect personal perceptions rather than the actual work environment. It is possible that workers who complained about psychosocial work conditions in their questionnaire responses did not do so in the presence of colleagues and supervisor during the interviews. Another explanation for the differences found could be that the interviews included workers who did not return their questionnaires.

At the individual level, psychosocial work characteristics were not strongly (rate ratios ranging from 0.95 to 1.11) related to sickness absence. In accordance with previous studies, we found a relationship between coworker support and sickness absence. Melchior et al. [6] reported poor workplace social support to be associated with increased rates of short, medium and long absence among men only. Moreau et al. [8] found that low social support at work is predictive of sick leave in both sexes. Our results showed that low coworker support was associated with higher rates of long duration absence but the height of the rate ratio raises questions on the clinical importance of this finding. Nielsen et al. [20] concluded that low supervisory support predicted short and long episodes of sickness absence in men but not in women. We could not confirm an association between supervisor support and sickness absence in our study.

Lack of job control was found to explain 12% of registered sick leave days in a 2-year follow-up of 1919 Danish workers [21]. Many studies have reported low levels of job control to be related to more frequent and longer absences. We found no relationship between sickness absence and job control at the individual level, although there were indications that a self-reported combination of high demands and low control was related to sickness absence with borderline significance. Job control independently assessed at the workplace level was related to sickness absence, as absence rates were higher in the department with less control over work.

Identification of distressing work environments is necessary to devise and implement interventions to reduce distress and prevent or minimize resulting sickness absence. The finding that psychosocial work conditions assessed at the workplace level were associated with sickness absence suggest that workplace oriented interventions to improve the psychosocial work environment could influence absence levels. Bond and Bunce [22] tested whether a work reorganization intervention could reduce job stress by increasing the employee's job control. The intervention significantly improved mental health, sickness absence rates and self-rated performance after a 1-year follow-up. Our results support the importance of the control dimension as the department with combined high demands and low control had higher rates of absence, and in particular long duration sickness absence.

The role of the supervisor in workplace interventions remains to be investigated. Using departments of a sales and services company as unit for randomization, Kawakami et al. [23] performed a controlled trial to determine the effects of supervisor training on mental health at work. They failed to show a clear effect on reduction of job stress, but concluded that the intervention may be useful for maintaining worker autonomy and improving the friendliness of the workplace atmosphere. In our study, employees working in department C perceived more supervisor support than the reference group. Although supervisor support was not related to individual sickness absence, it is possible that it buffered the adverse effects of self-perceived high demands and low control in this department.

This study showed that self-reported psychosocial work conditions were not significantly related to sickness absence and differed from such conditions assessed at the workplace level. The department with combined high demands and low control had higher rates of short and particularly long absences. The fact that psychosocial work conditions and their relationship with sickness absence depended on the level and manner of assessment of the former warrants more multilevel studies on psychosocial work environments.


Key points
  • Self-assessed job demands, job control and their combination were not significantly related to sickness absence.
  • Employees had higher rates of short and particularly long episodes of absence in the department in which demands were high and control over work low.
  • The differing results of assessing psychosocial work conditions at the individual and the workplace level might explain the inconsistent findings in literature on the relationship of these conditions with sickness absence. This warrants more multilevel studies.

 


   Conflicts of interest
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conflicts of interest
References
 
None declared.


   Acknowledgements
 
The authors wish to thank Liesbeth de Boer, occupational health psychologist, for performing the interviews of which the results were used in this study as a measure for psychosocial characteristics at the workplace level.


   References
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conflicts of interest
 References
 

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  5. Niedhammer I, Bugel I, Golsberg M, Leclerc A, Guéguen A. Psychosocial factors at work and sickness absence in the Gazel cohort: a prospective study. Occup Environ Med (1998) 55:735–741.[Abstract/Free Full Text]

  6. Melchior M, Niedhammer I, Bergman LF, Goldberg M. Do psychological work factors and social relations exert independent effects on sickness absence? A six year prospective study of the GAZEL cohort. J Epidemiol Community Health (2003) 57:285–293.[Abstract/Free Full Text]

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  8. Moreau M, Valente F, Mak R, et al. Occupational stress and incidence of sick leave in the Belgian workforce: the Belstress study. J Epidemiol Community Health (2004) 58:507–516.[Abstract/Free Full Text]

  9. Landsbergis P, Theorell T, Schwartz J, Greiner BA, Krause N. Measurement of psychosocial workplace exposure variables. Occup Med (Lond) (2000) 51:163–188.

  10. 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.[CrossRef][Web of Science][Medline]

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  14. Notelaers G, van Veldhoven M, Vermunt J. Towards a methodology for counteracting stress at work. Risk analysis with a standardized questionnaire. (2002) Proceedings of the XVIth World Congress on Occupational Health and Safety, Austrian Workers' Compensation Board, Vienna.

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  17. Drenth JD, Sijtsma K. Introduction into the theory of psychological tests and their applications. Houten, The Netherlands: Bohn, Stafleu & Van Loghum, 1990.

  18. van Rhenen W, Schaufeli WB, van Dijk FJH, Blonk RWB. Coping and sickness absence. Int Arch Occup Environ Med (2008) 81:461–472.[CrossRef]

  19. North FM, Syme SL, Feeney A, Shipley M, Marmot M. Psychosocial work environment and sickness absence among British civil servants: the Whitehall II study. Am J Public Health (1996) 86:332–340.[Abstract/Free Full Text]

  20. Nielsen ML, Rugulies R, Christensen KB, Smith-Hansen L, Kristensen TS. Psychosocial work environment predictors of short and long spells of registered sickness absence during a two-year follow-up. J Occup Environ Med (2006) 48:591–598.[CrossRef][Web of Science][Medline]

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  23. Kawakami M, Takao S, Kobayashi Y, Tsutsumi A. Effects of web-based supervisor training on job stressors and psychological distress among workers: a workplace-based randomized control trial. J Occup Health (2006) 48:28–34.[CrossRef][Web of Science][Medline]


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