P2-36 Body mass index and risk of incident ischaemic heart disease in women: a prospective cohort study

Background Various studies have examined body mass index in relation to mortality due to ischaemic heart disease (IHD), but few data are available on incident IHD including non-fatal events particularly in women. Methods We used multivariate Cox regression, taking into account confounding and mediating factors, to examine the association between body mass index and first IHD event (ascertained from hospital records and death registration) in the Million Women Study, a population-based prospective cohort of middle age British women. Results In this cohort of women aged 50–70 years, there were 48 895 incident IHD events during 10.7 million person-years of follow-up, including 5108 deaths with IHD identified as the primary cause. IHD incidence rate was 2.1 per 100 women per 5 years. Mean measured BMI (SD) was 26.7 (4.7) kg/m2. Risk for IHD increased with higher BMI (p<0.001). The large number of incident IHD events in this cohort makes it possible to examine in detail possible effect modification by other risk factors, including comparing associations between current and never smokers, or by socioeconomic status or physical activity level. Conclusion Non-fatal IHD adds considerably to the burden of heart disease. In this very large prospective study, incident IHD in women was strongly associated with excess weight.