The socioeconomic gradient in the incidence of stroke - A prospective study in middle-aged women in Sweden

Background and Purpose-A socioeconomic gradient in stroke has been demonstrated in a variety of settings, but mostly in men. Our purpose was to establish whether a socioeconomic gradient in stroke existed in a group of Swedish women and whether this gradient could be explained by established stroke risk factors or psychosocial factors. Methods-The Women's Lifestyle and Health Cohort Study includes 49 259 women from Sweden aged 30 to 50 years at baseline (1991 to 1992). The women completed an extensive questionnaire and were traced through linkages to national registries until the end of 2002. Among the 47 942 women included in these analyses, there were 200 cases of incident stroke during follow up (121 ischemic stroke, 47 hemorrhagic stroke, and 32 of unknown origin). Statistical analysis was through the Cox proportional hazards model. Results-The risk of stroke was significantly inversely related to years of education completed, our proxy for socioeconomic status (hazard ratio comparing lowest with highest education group=2.1, 95% CI: 1.4 to 2.9, P for trend < 0.001). This association was reduced after adjustment for established risk factors, although remaining significant (1.5, 1.0 to 2.2, P for trend=0.04). The gradient was more pronounced for ischemic stroke (2.9, 1.8 to 4.7, P for trend < 0.001) than for hemorrhagic stroke (1.4, 0.7 to 2.9, P for trend=0.35). Job strain and social support were unrelated to risk of stroke. Self-rated health was strongly related to risk of stroke mediated by established risk factors. Psychosocial factors did not contribute toward the socioeconomic gradient in stroke. Conclusions-There was a strong gradient in risk of stroke by years of education, especially for ischemic stroke. Most of the social gradient was explained by established risk factors, particularly smoking and alcohol, but not by psychosocial factors.