Determinants of social inequalities in stroke incidence across Europe: a collaborative analysis of 126 635 individuals from 48 cohort studies

Background Knowledge on the origins of the social gradient in stroke incidence in different populations is limited. This study aims to estimate the burden of educational class inequalities in stroke incidence and to assess the contribution of risk factors in determining these inequalities across Europe. Materials and methods The MORGAM (MOnica Risk, Genetics, Archiving and Monograph) Study comprises 48 cohorts recruited mostly in the 1980s and 1990s in four European regions using standardised procedures for baseline risk factor assessment and fatal and non-fatal stroke ascertainment and adjudication during follow-up. Among the 126 635 middle-aged participants, initially free of cardiovascular diseases, generating 3788 first stroke events during a median follow-up of 10 years, we estimated differences in stroke rates and HRs for the least versus the most educated individuals. Results Compared with their most educated counterparts, the overall age-adjusted excess hazard for stroke was 1.54 (95% CI 1.25 to 1.91) and 1.41 (95% CI 1.16 to 1.71) in least educated men and women, respectively, with little heterogeneity across populations. Educational class inequalities accounted for 86-413 and 78-156 additional stroke events per 100 000 person-years in the least compared with most educated men and women, respectively. The additional events were equivalent to 47%-130% and 40%-89% of the average incidence rates. Inequalities in risk factors accounted for 45%-70% of the social gap in incidence in the Nordic countries, the UK and Lithuania-Kaunas (men), but for no more than 17% in Central and South Europe. The major contributors were cigarette smoking, alcohol intake and body mass index. Conclusions Social inequalities in stroke incidence contribute substantially to the disease rates in Europe. Healthier lifestyles in the most disadvantaged individuals should have a prominent impact in reducing both inequalities and the stroke burden.