Background: Social inequalities in the incidence of type 2 diabetes and the relation of health behaviors and psychosocial factors to the incidence of type 2 diabetes are not well established.
Methods: Prospective occupational cohort study of 10 308 civil servants aged 35 to 55 years at baseline in phase 1 (1985-1988). Diagnosis of diabetes was ascertained by questionnaire at baseline and follow-up at phases 2 (1989), 3 (1992-1993), 4 (1995), and 5 (1997-1999) and glucose tolerance tests in phases 3 and 5.
Results: Participants working in the lower employment grades had a higher incidence of diabetes than those in higher employment grades (men: odds ratio [OR], 2.9; 95% confidence interval [CI], 1.9-4.4; women: OR, 1.7 [95% CI, 0.8-3.7]). Body mass index and other risk factors considered traditional for type 2 diabetes were found to be so in this cohort. In men, of the psychosocial risk factors examined, only effort-reward imbalance was related to incidence of diabetes (OR, 1.7 [95% CI, 1.0-2.8]). The General Health Questionnaire depression subscale was related to incidence of diabetes and impaired glucose tolerance (OR, 1.25 [95% CI, 1.0-1.6]). These associations remained after adjustment for other confounding factors. In men only, social difference in incidence of diabetes was reduced but still significant after adjustment for conventional risk factors.
Conclusions: An inverse relationship exists between social position and incidence of diabetes that is partly explained by health behaviors and other risk factors. Effort-reward imbalance, which is reportedly associated with coronary heart disease, is also associated with type 2 diabetes.