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.
- social inequalities
- social epidemiology
- cohort studies
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Contributors MMF and GV conceived the research and drafted the manuscript, with the contribution of FK, LEC, KK, TJ and HT-P. GV conducted the statistical analyses. KK directs the MORGAM Project and is the overall guarantor of the MORGAM data. PA, DA, MB, GC, WD, JF, SG, LI, YN, APa, APe, VS, SS, AT and TW actively contributed to the interpretation of the results and made critical revision of the manuscript drafts for important intellectual content. MMF, FK, TJ, PA, DA, GC, WD, JF, SG, LI, YN, APa, APe, VS, SS, AT, TW and HT-P are responsible for data collection.
Funding This work was supported by the MORGAM Project’s recent funding: European Community FP 7 projects CHANCES (HEALTH-F3-2010-242244) and BiomarCaRE (HEALTH-F2-2011-278913). These grants supported central coordination, workshops and part of the activities of the MORGAM Data Centre, at THL in Helsinki, Finland. MORGAM participating centres are funded by regional and national governments, research councils, charities and other local sources.
Competing interests GV work was supported by the European Community FP7 project BiomarCaRE (HEALTH-F2-2011-278913). KK received support from the European Union (HEALTH-F3-2010-242244; HEALTH-F2-2011-278913). AP was supported by a Grant from the Polish State Committee for the Scientific Research and received personal fees from Amgen and Sanofi outside this submitted work. VS was supported by the Finnish Foundation for Cardiovascular Research. The remaining authors declare no conflict of interest. The sponsors had no role in the study design; in the collection, analysis and interpretation of data; in the writing of the report; and in the decision to submit the article for publication.
Ethics approval Each MORGAM participating centre is responsible for ethical approval and patient consent, according to local rules at the time of study enrolment.
Provenance and peer review Not commissioned; externally peer reviewed.
Author note A tribute to dr. Giuseppe Ferrario, a pioneer of neuroepidemiology, who in the early 1800s documented the socio-economic gradient in stroke in Milan (Neurology 2012;79(10):1056-9)
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