The European Journal of Public Health Advance Access originally published online on September 14, 2005
The European Journal of Public Health 2006 16(5):470-475; doi:10.1093/eurpub/cki190
Miscellaneous |
Retaining the ability to work—associated factors at work*
Per Lindberg1, Eva Vingård1,2, Malin Josephson1,2 and Lars Alfredsson3,4
1 Department of Clinical Neuroscience, Section for Personal Injury Prevention, Karolinska Institutet, Stockholm, Sweden
2 Department of Medical Sciences, Section of Occupational and Environmental Medicine, Uppsala University, Sweden
3 Division of Cardiovascular Epidemiology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
4 Centre of Public Health, Stockholm County Council, Stockholm, Sweden
Correspondence: Per Lindberg, Section for Personal Injury Prevention, Karolinska Institutet, Box 12718, SE-112 94 Stockholm, Sweden, tel: +46 8 692 22 74; fax: +46 8 653 94 13, e-mail: per.lindberg{at}cns.ki.se
Received January 17, 2005, accepted August 12, 2005
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Abstract |
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Background: Prevention of work-related sickness absence has traditionally dealt with reduction of exposures to known risk factors. However, there is reason to believe that there are also factors at work that act as health supportive. This study aimed to identify workplace factors predicting retained work ability. Methods: The present prospective cohort study included the follow-up of 6337 randomly chosen, gainfully employed Swedish women and men for 1 year. Uni- and multivariate logistic regression analyses odds ratios (ORs) together with 95% confidence interval were calculated in order to estimate the strength of the associations between different factors reported in a baseline questionnaire, and retained work ability was defined as not being on long-term sick leave (>14 days) during the follow-up. Results: Work-related factors significantly associated with retained work ability were as follows: reporting the work as physically non-strenuous (women: OR 1.6; men: OR 2.1), working at a workplace where there are no plans to close down (w: OR 2.3) and feeling recuperated and full of energy (w := R1.5), and often being in the mood for work (m : 1.4). Significant associations with retained work ability were also found for age, socioeconomic level, household composition, employment sector, and previous sick leave patterns. Conclusion: The findings highlight some factors at work, but also some in the personal sphere that are influential for retained work ability, regardless of sick leave patterns prior to the study period. Identifying such factors can provide valuable knowledge for workplace health promotion.
Keywords: health promotion, salutogenic, sick leave, work ability, work factors
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Background |
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An increasing number of empirical studies demonstrate associations between different factors related to working, as well as to personal life and sickness absence.1–8 Sickness absence is a complex phenomenon and not necessarily the same as the health status of the individual or sickness in a society.9 Sick leave is better understood as an interplay between the individual's health contra the social insurance system; levels of benefits; type of work; flexibility at work by lowered working capacity; attitudes towards work; and other medical; social; and psychological factors.1,10,11 Though sickness absence has been pointed out as a strong predictor of future sickness absence12,13 only few of these recently published studies have controlled for sick leave prior to the study period.3,14 It should be pointed out that controlling for previous sick leave is not directly comparable with controlling for more frequently used parameters such as pre-existing morbidity, including analyses stratified by a relevant health marker, or following a cohort that is initially ‘healthy’ at the baseline.
For the individual, the workplaces, and the society, there would be considerable gains if the number of people on sick leave could be reduced. Traditionally this has been done by elimination/reduction of identified risk factors at work. This is still the first choice in order to achieve a sustainable working life. However, sometimes, due to costs, practical problems or no immediate solution at the moment, it is not possible to do this. It would in general, and especially in these cases, be of great value if the employees could be ‘strengthened’ to retain their work ability through other measures. How is it that some people exposed to well known risks do not get sick-listed and some do? Is it just genetics? Our hypothesis is that there also are factors at work that act as predictors of not being on sick leave, in this study called ‘retained work ability’. Identifying and promoting such factors could be an additional tool to reduce the number of sick leave days. We have found no other study that explicitly addresses this, even when identifying such factors could be of significance for targeted workplace health promotion. Thus, the main aim of this study was to find factors at work, predicting retained work ability among gainfully employed persons, by controlling for previous sick leave patterns.
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Methods |
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Design and subjects
The present study was designed as a cohort study with a 1-year follow-up. The study population, 12 034 men and women aged 35, 45, and 55 years, was randomly chosen from the Swedish national population register at Statistics Sweden in 2000. At the baseline the subjects received a postal questionnaire. Two reminders were distributed within 4 weeks. The response rate was 65% (women 69%, men 60%) corresponding to a total of 7806 respondents. Analysis of the dropouts showed a somewhat lower response rate among low-income earners (53%), singles (58%), and subjects not born in Sweden (50%).
Inclusion criteria for this study were full-time (
35 h/week) working women and men and part-time working women, being employees or self-employed, and having at no time received any degree of early retirement pension or disability pension. A total of 1469 subjects who had answered the questionnaire were excluded; of these, 917 were not working, 157 men worked part-time, 139 individuals had been granted early retirement or disability pension, and for 256 there were missing data on sickness absence in the year prior to the survey. Part-timers among men were excluded as, in contrast to women, ill health is considered to be a main reason for not working full-time. This made a total of 6337 individuals: 3390 women and 2947 men. Sociodemographic features of the study population at the baseline are shown in table 1.
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Potential explanatory exposures
The analyses included exposure assessments using questions and scales tested and used in previous occupational research,15–18 demonstrating associations with ill-health. These independent variables, displayed in table 2, were chosen to cover sociodemographic factors, sick leave, labour market situation and terms of employment, physical work, psychosocial work factors, and work organisation. The variables were dichotomised into exposed–unexposed, where exposed was expected to denote a health-supportive exposure level according to hypotheses by the authors. In order to control for sick leave prior to the survey the respondents were divided into three groups according to their self-reported frequency of sick leave during the 12 months preceding the survey. For the respondents who reported that they had neither been on any sick leave nor taken days of holiday or compensatory leave instead of reporting sick the heading was ‘no previous sick leave’ (n = 2965, w: 1413; m: 1552). The respondents with one spell of sick leave and/or days of holiday or compensatory leave instead of sick leave were designated ‘on sick leave once previously’ (n = 2225, w: 1284; m: 941). The respondents who reported two or more spells of sick leave were labelled ‘on sick leave twice or more previously’ (n = 1147, w: 693; m: 454).
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Follow-up
The follow-up of the respondents were carried out for 1 year with regard to spells of long-term sick leave, defined as >14 days. Data concerning this was obtained from a register at the National Insurance Board in Sweden, which includes sick leave data for all Swedish residents with spells of sick leave >14 days. The outcome was retained work ability defined as not having any spell of sick leave >14 days during the follow-up. This was true for 82% of the women and 89% of the men.
Statistics
Odds ratios (ORs) together with 95% confidence interval (95% CI) were calculated in order to estimate the strength of the associations between different factors at the baseline and retained work ability during the follow-up. Uni- and multivariate logistic regression analyses were carried out for each gender separately. The same multivariate model was used for women and men, and included all factors in the univariate analyses that, either for women or for men, were associated with retained work ability with a point estimate 1.2 and a lower bound of the CI 1.0. In the multivariate model the associations were adjusted for age, social and economic factors, employment sector, and sickness absence during the year prior to the survey.
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Results |
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The results of the crude and of the adjusted analyses are displayed in table 3. Most of the associations found in the crude analyses were attenuated in the multivariate analyses, indicating some correlations between the included variables. The results did not point out any significant gender differences in the associations between baseline exposures and retained work ability during the follow-up, neither in the crude nor in the multivariate analyses. The CIs for all associations were overlapping. Exposures that, either for women or for men, showed statistically significant associations in the adjusted analyses will be described as follows.
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Workplace factors in the multivariate analysis that were associated with retained work ability during the follow-up were as follows: reporting the work as physically non-strenuous (women: OR 1.6, 95% CI 1.3–1.9; men: OR 2.1, 95% CI 1.5–2.8), working at a workplace where there are no plans to close down (w: OR 2.3, 95% CI 1.3–4.2; m: OR 0.7, 95% CI 0.2–2.0), and often being in the mood for work (w: OR 1.1, 95% CI 0.8–1.4; m: OR 1.4, 95% CI 1.0–2.0).
Factors of importance in order to retain work ability were as follows: feeling recuperated when starting the work and full of energy during the working day (w: OR 1.5, 95% CI 1.1–1.9; m: OR 1.2, 95% CI 0.9–1.7), as well as the pattern of sick leave during the year preceding the survey. Retained work ability during the follow-up was associated with no (w: OR 2.7, 95% CI 2.1–3.5; m: OR 2.6 95% CI 1.8–3.7) or only one (w: OR 1.6, 95% CI 1.2–2.0; m: OR 1.9, 95% CI 1.3–2.7) spell of sick leave during the year prior to the survey compared with those who had two or more spells.
There were further associations with retained work ability for women and men who were <55 years of age, had more than 11 years of schooling, had good personal finances, lived together with another adult and child(-ren) compared with other ways of cohabiting, or lived alone, and had an employer other than the local authorities.
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Discussion |
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Sick leave, as well as retained work ability, is a complicated matter, and not a mere question of health status. It is also influenced by whether or not it is possible to adjust work demands and working conditions according to the individual's needs.1,9–11 This is an issue that is not solely concerned with the nature of the work, but also with the attitudes of management, superiors, and co-workers. The present findings support our hypothesis that there are factors at work predicting retained work ability.
According to this study, one of the most important factors for subjects to retain their work ability during the follow-up was having a physically non-strenuous job. This is in line with what Borg et al.19 found by investigating work environment and changes in self-rated health, and with Voss et al.20 who found a lower incidence of sickness among both women and men who did not complain about heavy lifting and monotonous movements. The beneficial association between physically non-strenuous work and retained work ability remained, even after adjusting for previous sick leave, socioeconomic level, employment sector, and age.
As other studies have reported that social support from the supervisor has a positive influence on well-being21 and reduces the level of absence without a doctor's certificate,22 it seemed plausible to expect an association in this direction also in our study. However, we found a weak support for this. It is possible that if we had looked at the first 7 days of sick leave, for which no doctor's certificate is required in Sweden, we would also have found an influence of social support from the manager on sick leave. But as we investigated longer spells of sick leave, the level of social support from the superior was perhaps not enough to buffer against the adverse effects of other factors. However, often being in the mood for work was associated with retained work ability during follow-up. This could be an indication of job satisfaction and that the individual's personal capacity, mentally as well as physically, was in line with the work tasks, but also that there was a good ‘climate’ at the workplace.
The secure feeling of working at a place with no plans for closure had an influence on the working ability (or retained work ability). It has been shown that job insecurity is strongly associated with poor self-rated health and minor psychiatric morbidity, for both the sexes.23–25 Similar results were found in a study examining downsizing of organisations, where the major downsizing was associated with an increase in sickness absence among permanent employees but not among temporary employees.26 Without being able to draw conclusions about causal pathways a recent study found an association between moderate downsizing (women and men) and considerable expansion (women), respectively, and increased risk of long-term (90 days) sickness absence.27
According to the results of the present study, the probability of retained work ability during follow-up was greater among both women and men employed in the private sector, the county councils or the government compared with those employed by local authorities. Explanations for this finding could be that organisations other than local authorities offer jobs with other demands, better working conditions, and are better organised in terms of rehabilitation and facilitating staying at work. However, it could also be that the local authorities do not dismiss people so quickly. As a matter of fact, there is an overrepresentation of employees on long-term sick leave (>60 days) in the public sector compared with the private sector.28
Going to work recuperated and feeling full of energy throughout the working day predicted retained work ability. This is in line both with a study on teachers, which, although it was cross-sectional, showed that non-recuperated subjects had a higher level of sickness absence as well as sickness presenteeism,29 and also with two other studies concerning the need for recovery after work as a predictor for sickness absence.2,3
Not having any sick leave during the year preceding the survey was in itself a predictor of retained work ability during the follow-up. This highlights that every effort that is made to reduce the number of sick leave spells (i.e. not only long-term spells) is important, as it will limit the future sick leave. In addition, this also implies that the work-related findings in this study are applicable regardless of previous reasons and patterns in connection with sick leave, which could be an advantage with regard to achieving higher precision in interventions.
Methodological considerations
This study was set up to study the factors at work that are associated with retained work ability. The subjects were all aged 35, 45, or 55, as they were chosen from a study that amongst other aspects studied attitudes to the social insurance system, with the aim of checking whether these attitudes were dependent on age.30 The age structure of this study makes the results somewhat less suited for generalisations. But as our age groups cover the most active years in working life we do not suspect that the results would have been very different with a traditional random selection among the 20- to 64-years-olds.
The response rate, 65%, raises questions about how reliable the results are. The prevalence data at the baseline could be skewed by selection. We have controlled for this as far as possible by adjusting the analyses for sociodemographic factors, labour market issues, and previous sick leave. In order to see how stable the main results were the ‘worst-scenarios’ were calculated, as if the response rate had been 100%. This showed that at least 60% of the missing women and 67% of the missing men would have had to report physically strenuous workload and yet retaining their work ability during the follow-up in order to eliminate the associations found between workload and retained work ability. This distribution of exposure and retained work ability is extremely unlikely.
As this is an explorative study, and we found no empirical cut-off points for the positive end of the independent variables to rely on, we had to, based on our hypotheses on what could be health supportive, test the included variables at different cut-offs in order to find the least positive exposures needed to retain work ability. The ground for this was that such levels are easier to be implemented and can still be health supportive. These levels have to be confirmed in further studies.
The results of the crude analyses were almost all attenuated in the multivariate analyses, which is a normal finding especially when the variables are associated with the same area. Initially conducted analyses showed only weak correlations between most of the included independent variables, somewhat more pronounced correlation for ‘often in the mood for work’ with ‘satisfied with own performance’ and ‘recuperated’, and ‘appreciation by superior’ with ‘satisfied with own performance’ and ‘good leadership’. A limitation is that the determinants included in this study all stem from a pathogenic approach and there is not enough empirical evidence if they also are suited for a salutogenic approach. Further studies on retained work ability would benefit from also including determinants designed for a salutogenic approach.
Another problem is that sickness absenteeism predicts future absenteeism12,13 and people with health problems influencing their work capacity are more inclined to experience their working conditions as more strenuous than the healthy persons would. We have considered this in the multivariate analyses by controlling for self-reported sick leave patterns during the year preceding the survey. In an earlier stage we also performed stratified analyses for the same three groups with their differing sick leave patterns as used here for controlling, but we found very little difference between the groups regarding work factors associated with retained work ability. Unfortunately we have no means of checking the validity of the self-reported sick leave. Earlier studies31–33 have found low sensitivity for self-reported data on sick leave; whereas, a recent study34 reported a relatively good agreement between the annual numbers of self-reported and recorded sickness absence days in both the sexes. In the present study a low sensitivity for self-reported data on sick leave might have resulted in some individuals who had been on sick leave being classified as having had ‘no previous sick leave’. Such misclassifications due to recall bias, if non-differential, will dilute the results and lead to an underestimation of the association between previous sick leave and retained work ability during the follow-up. On the other hand, one of the strengths of this study is that there is practically no misclassification of the outcome measure, as all sick leave spells >14 days are registered in Sweden. Such registration is necessary in order to avail sickness benefits. Spells >14 days were chosen as these are the only ones that are registered, but also in order not to include sick leaves due to common illnesses, such as cold and influenza.
Our study was based on the information given by study subjects at the baseline, and the follow-up was done by means of the register data. Hence we had no information about changes in exposure during the study period. The study persons could have changed their work tasks or even the employer. We cannot rule out that this could have contributed to a certain selection into and out of occupations. People in too physically and/or mentally demanding jobs will perhaps tend to leave for a more suitable job with fewer negative exposures and less risk of sick leave, and thus dilute the associations. On the other hand, during a 1-year follow-up there is not such a big turnover of the staff that it will jeopardise the results. For example, the rate of job termination in Sweden in 2001 was 
3% among the permanently employed people, who constitute roughly 84% of all those who are gainfully employed.35
We were not able to adjust the studied associations for lifestyle factors, e.g. smoking, which is considered a major health threat. In Sweden, however, the overall prevalence of daily smoking is only 18%,36 and adjusting for this would probably not have changed our results substantially.
In conclusion, the results of this study suggest that, regardless of the gender and sick leave patterns prior to the study period, work-related factors, such as physically non-strenuous work, and some psychosocial work factors, such as being in the mood for work, having a secure employment, and being recuperated and full of energy during the working day, can be influential for retaining the working ability. Identifying such factors will provide valuable knowledge for workplace health promotion in order to prevent long-term sick leave.
Key points
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Acknowledgments |
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The authors thank Max Köster, statistician at the Swedish National Board of Health and Welfare, for conducting the statistical analyses, and the Swedish government commissions SOU 2000:121 and SOU 2002:5 for initiating and financing the data collection.
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Footnotes |
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* This study has earlier been presented orally at the ‘2nd International Symposium on Work Ability’ (ICOH/IEA), 18–20 October 2004, Verona, Italy.
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References |
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1 Alexandersson K. Sickness absence: a review of performed studies with focused on levels of exposures and theories utilized. Scand J Soc Med 1998;26:241–9.[Web of Science][Medline]
2 de Croon EM, Sluiter JK, Frings-Dresen MHW. Need for recovery after work predicts sickness absence: a 2-year prospective cohort study in truck drivers. J Psychosom Res 2003;55:331–9.[CrossRef][Web of Science][Medline]
3 Janssen N, Kant I, Swaen GMH, et al. Fatigue as a predictor of sickness absence: results from the Maastricht cohort study on fatigue at work. Occup Environ Med 2003;60:i71–6.
4 Melchior M, Niedhammer I, Berkman LF, Goldberg M. Do psychosocial 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;57:285–93.
5 Piirainen H, Räsänen K, Kivimäki M. Organizational climate, perceived work-realted symptoms and sickness absence: a population-based survey. J Occup Environ Med 2003;45:175–84.[Web of Science][Medline]
6 Virtanen M, Kivimaki M, Elovainio M, et al. From insecure to secure employment: changes in work, health, health related behaviours, and sickness absence. Occup Environ Med 2003;60:948–53.
7 Hensing G, Alexanderson K. The association between sex segregation, working conditions, and sickness absence among employed women. Occup Environ Med 2004;61:7e.
8 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 2004;32 (Suppl 63):49–108.
9 Alexanderson K, Leijon M, Åkerlind I, et al. Epidemiology of sickness in a Swedish county in 1985, 1986 and 1987. Scand J Soc Med 1994;22:27–34.[Web of Science][Medline]
10 Kristensen T. Sickness absence and work strain among danish slaughterhouse workers: an analysis of absence from work regarded as coping behaviour. Soc Sci Med 1991;32:15–27.[CrossRef][Web of Science][Medline]
11 Marmot M, Feeney A, Shipley M, et al. Sickness absence as a measure of health status and functioning: from the UK Whitehall II study. J Epidemiol Community Health 1995;49:124–30.
12 Smulders P, Nijhuis F. The job demands-job control model and absence behaviour: results of a 3-year longitudinal study. Work Stress 1999;13:115–31.
13 Vahtera J, Pentti J. The effect of objective job demands on registered sickness absence spells; do personal, social and job-related resources act as moderators? Work Stress 1996;10:286–308.[CrossRef][Web of Science]
14 Kivimäki M, Elovainio M, Vahtera J. Workplace bullying and sickness absence in hospital staff. Occup Environ Med 2000;57:656–60.
15 Stockholm County Council (Sweden). Hälsa och hållbart arbetsliv i Stockholms län [Health and sustainable working life in Stockholm county]. Stockhlom: Department of occupational and environmental health, Stockholm County Council, 2001.
16 Borg G. Borg's perceived exertion and pain scales. USA: Human Kinetics, 1998.
17 Karasek R, Töres T. Healthy Work. Stress, productivity, and the reconstruction of working life. New York: Basic Books, 1990.
18 Waldenström M, Theorell T, Ahlberg-Hulthén G, et al. Assessment of psychological and social current working conditions in epidemiological studies: experiences from the MUSIC-Norrtälje study. Scand J Public Health 2002;30:94–102.[CrossRef][Web of Science][Medline]
19 Borg V, Kristensen T, Burr H. Work environment and changes in self-rated health: a five-year follow-up study. Stress Med 2000;16:37–47.[CrossRef][Web of Science]
20 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;58:178–84.
21 Lu L. Work motivation, job stress and employees' well-being. J Appl Manag Studies 1999;8:61–72.
22 Tharenou P. A test of reciprocal causality for absenteeism. J Organ Behav 1993;14:269–90.
23 Ferrie JE, Shipley MJ, Stansfeld SA, Marmot MG. Effects of chronic job insecurity and change in job security on self reported health, minor psychiatric morbidity, physiological measures, and health related behaviours in British civil servants: the Whitehall II study. J Epidemiol Community Health 2002;56:450–4.
24 D'Souza RM, Strazdins L, Lim LL-Y, et al. Work and health in a contemporary society: demands, control, and insecurity. J Epidemiol Community Health 2003;57:849–54.
25 Virtanen P, Vahtera J, Kivimaki M, et al. Employment security and health. J Epidemiol Community Health 2002;56:569–74.
26 Vahtera J, Kivimaki M, Pentti J, et al. Organisational downsizing, sickness absence, and mortality: 10-town prospective cohort study. BMJ 2004;328:555.
27 Westerlund H, Ferrie J, Hagberg J, et al. Workplace expansion, long-term sickness absence, and hospital admission. Lancet 2004;363:1193–7.[CrossRef][Web of Science][Medline]
28 Riksförsäkringsverket. Långtidssjukskrivna—diagnos, yrke arbetsgivare och återgång i arbete [Long-term sicklisted—diagnosis, employer and return to work]. Report No. RFV redovisar 2001. Stockholm: The National Social Insurance Board, 2001:11.
29 Aronsson G, Svensson L, Gustafsson K. Unwinding, recuperation, and health among compulsory school and high school teachers in Sweden. Int J Stress Manag 2003;10:217–34.[CrossRef]
30 Vingård E, Lindberg P. Hälsa, arbetsförhållanden, sjukfrånvaro och sjuknärvaro bland män och kvinnor födda 1945, 1955 och 1965. [Health, working conditions, sick leave and sickness attendance among men and women born in 1945, 1955 and 1965]. In: SOU 2000:121 Sjukfrånvaro och sjukskrivning—fakta och förslag. Slutbetänkande av Sjukförsäkringsutredningen. [SOU 2000:121 Sick leave and reporting sick—facts and proposals. Final report from The Commission on Health Insurance.]. Stockholm: Socialdepartementet [The Ministry of Health and Social Affairs], 2000: 303–72.
31 Burdorf A, Post W, Bruggeling T. Reliability of a questionnaire on sickness absence with specific attention to absence due to back pain and respiratory complaints. Occup Environ Med 1996;53:58–62.
32 Severens JL, Mulder J, Leheij RJL, Verbeek ALM. Precision and accuracy in measuring absence from work as a basis for calculating productivity costs in The Netherlands. Soc Sci Med 2000;51:243–9.[CrossRef][Web of Science][Medline]
33 van Poppel MNM, de Vet HCW, Koes BW, et al. Measuring sick leave: a comparison of self-reported data on sick leave and data from company records. Occup Med 2002;52:485–90.[Abstract]
34 Ferrie JE, Kivimaki M, Head J, et al. A comparison of self-reported sickness absence with absences recorded in employers' registers: evidence from the Whitehall II study. Occup Environ Med 2005;62:74–79.
35 Statistics Sweden. Kortperiodisk sysselsättingsstatistik 1:a kvartalet 2001 [Short-term employment 1st quarter of 2001]. Report No. AM 63 SM 0102. Stockholm: Statistics Sweden, 2001.
36 The National Institute of Public Health in Sweden. Smoking habits. Available at: http://www.fhi.se/omfhi/verksmhet_tobak.asp#Rökning. Accessed 28 February, 2003.
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