Explanations of socioeconomic differences in excess risk of type 2 diabetes in Swedish men and women

OBJECTIVE: We investigated to what extent socioeconomic differences in type 2 diabetes risk could be explained by established risk factors (obesity, physical inactivity, smoking, and heredity) and psychosocial factors (low decision latitude at work and low sense of coherence). RESEARCH DESIGN AND METHODS: This cross-sectional study comprised 3,128 healthy Swedish men and 4,821 women, aged 35-56 years, living in the Stockholm area. An oral glucose tolerance test identified 55 men and 52 women with type 2 diabetes. The relative contribution of established and psychosocial factors to socioeconomic differences in diabetes risk was assessed by comparing analyses with adjustment for different sets of these factors. RESULTS: The relative risks (RRs) for type 2 diabetes in middle and low socioeconomic groups in men were 2.4 (95% CI 1.0-5.3) and 2.9 (1.5-5.7), respectively, and in women 3.2 (1.5-6.6) and 2.7 (1.3-5.9), respectively. In men, the RRs decreased to 1.9 (0.8-4.4) and 2.1 (1.0-4.2) after adjustment for established risk factors; no further change was found when psychosocial factors were included. In women, the RRs changed to 2.4 (1.1-5.2) and 1.6 (0.7-3.8) by including established risk factors and to 2.3 (1.0-5.1) and 1.9 (0.8-4.3) by inclusion of psychosocial factors. After adjustment for both established and psychosocial factors, the RRs were 1.4 (0.6-3.6) and 1.0 (0.4-2.5), respectively. CONCLUSIONS: In men, the excess risk of type 2 diabetes was partly explained by established risk factors (36-42%), whereas psychosocial factors had no effect. In women, most of the socioeconomic differences in type 2 diabetes were explained by simultaneous adjustment for established risk factors and psychosocial factors (81-100%).