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The Karasek Job Demand-Control model has as its central tenet the so-called 'strain hypothesis', stating that the most adverse health outcomes are to be expected in 'high strain' jobs characterized by high job demands and low job control. Later, this model was elaborated, stating that 'isolated' high strain workers experiencing low worksite social support are even more worse off. This is labelled the 'iso-strain hypothesis'. However, in the literature, the question was raised whether a high level of job control may (1) mitigate or buffer the effects of high job demands on psychological well-being, or alternatively whether (2) a high level of social support may buffer the negative impact of high strain on psychological well-being. In this study among 16 335 male workers and 5084 female workers in Belgium, four indicators of psychological well-being are considered: feelings of depression, feelings of fatigue, sleep problems and use of psychoactive drugs. Both in men and in women, the general strain hypothesis and the iso-strain hypothesis alike are corroborated regarding the cross-sectional associations adjusted for age, level of education and living situation. This is most clear with respect to feelings of depression, less so with respect to the use of psychotropic drugs. The buffer hypotheses however are definitely not supported by our data.

Psychosocial characteristics have been linked to coronary heart disease. In the Belgian Job Stress Project (1994-1999), the authors examined the independent role of perceived job stress on the short-term incidence of clinical manifest coronary events in a large occupational cohort. A total of 14,337 middle-aged men completed the Job Content Questionnaire to determine the dimensions of the extended job strain model, job demands, decision latitude, and social support. Jobs were categorized into high strain, low strain, active jobs, and passive jobs. During the 3-year follow-up, 87 coronary events were registered. At baseline, 17% of workers experienced high strain. Job demands and decision latitude were not significantly related to the development of coronary heart disease after adjustment for covariates. The 38% risk excess among subjects classified in the high-strain category did not reach statistical significance. However, coronary heart disease incidence was substantially associated with the social support scale independently of other risk factors, with an adjusted hazard ratio of 2.4 (95% confidence interval: 1.4, 4.0) between extreme tertiles. No convincing evidence for an association of job demands, decision latitude, or job strain with the short-term incidence of coronary heart disease was found. However, our study underscores the importance of a supportive social work environment in the prevention of coronary heart disease.

OBJECTIVES:In many studies, obesity has been associated with morbidity or mortality, but only a few have studied the relation between obesity and sick leave. Our aim is to analyse the independent effects of both adiposity and body fat distribution in relation to the 1-y incidence of sick leave in a large cohort of male and female workers covering a variety of occupations, taking into account a wide range of socio-demographic, behavioural and bioclinical variables. DESIGN AND SETTING: The baseline survey of the Belstress study was conducted in 25 companies across Belgium between 1994 and 1998. A cohort of 20 463 workers (15 557 males and 4906 females) aged 35-59 y was followed for absenteeism during 1 y. The 75th percentile of the distribution of the total annual sickness days was used as a cutoff to classify the workers with a high 1-y incidence rate of sick leave. The relation between sick leave and both obesity and body fat distribution assessed by the body mass index (BMI) and the waist circumference, respectively, was analysed by multivariate logistic regression models. RESULTS: Using a backward procedure based on the likelihood ratio, we found central abdominal fatness to be an independent predictor of sick leave in both genders (high sick-leave incidence and long spells), but not BMI. In men, the odds ratios was 1.31 (99% CI 1.12-1.52, Po0.0001) and in women it ranged from 1.32 (99% CI 1.03-1.70, P ¼ 0.005) to 1.47 (99% CI 1.14-1.90, Po0.0001). Two baseline covariables, respiratory problems and perceived health, are confounders or mediators. CONCLUSIONS: In this study, body fat distribution was associated with a high annual sick-leave incidence and long spells of sickness absence. If this link is reversible, employers may benefit from programs aiming at the prevention and treatment of central obesity.