| Summary: | BACKGROUND: As early as the 17th century diabetes was linked to psychosocial stressors, yet this association still remains elusive. The impact of psychosocial work stressors on diabetes is also unknown, as are the pathways involved. AIM: To investigate the prospective effect and impact of psychosocial work stressors on incident T2DM and elucidate direct and indirect pathways in this association. METHODS: Prospective analysis (1991-2004) among 5895 Caucasian middle-aged civil servants free from baseline diabetes in the Whitehall II cohort study. T2DM was ascertained by an oral glucose tolerance test supplemented by self-reports over four consecutive waves of data collection. The demand/control/support and effort-reward imbalance models were used to assess psychosocial work stressors. RESULTS: Job strain (high job demands/low job control), iso-strain (high demands/low control/low work social support) and effort-reward imbalance (high efforts/low rewards at work) are associated with 60% to 2-fold higher risk of T2DM among women but not men. This effect is higher among obese and lower socioeconomic position individuals. An estimated 35-44% of T2DM cases are attributed to psychosocial work stressors among exposed women, while 10-15% of all cases in the study population are estimated to result from exposure to work stressors, assuming a causal association. Biological factors (obesity, HDL-cholesterol and markers of inflammation) explain 1/3 of the effect of psychosocial work stressors on T2DM. CONCLUSIONS: The observed association between psychosocial work stressors and T2DM is internally valid, temporal and biologically plausible, thus most likely causal. The external validity is questionable however as the effect was observed among a very specific sample of white-collar, Caucasian female civil servants. Given the interaction with body weight status, reduction of psychosocial work stressors would offer some benefits in light of the huge impact of the growing obesity epidemic on T2DM. Even though cardiometabolic and inflammatory factors explain a substantial part of the psychosocial effect on T2DM, other novel mediating factors should be identified. These results should be confirmed by other studies, preferably experimental, with special attention on gender differences. Policies for reduction of psychosocial work stressors should be informed by findings from such studies.
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