Race- and sex-specific associations of obesity measures with ischemic stroke incidence in the Atherosclerosis Risk in Communities (ARIC) study

Abstract

Background and purpose: Studies have suggested differences in the association between obesity and ischemic stroke in black versus white populations. In this study, we explored ischemic stroke risk in relation to a variety of obesity measures by sex and race.

Methods: Using data from the Atherosclerosis Risk in Communities Study, we obtained information on body mass index, waist circumference, and waist-to-hip ratio from 13 549 black and white participants who were aged 45 to 65 years between 1987 and 1989. All were free of cardiovascular disease and cancer at baseline. Incident strokes over a median follow-up of 16.9 years were ascertained from hospital records.

Results: Although crude incidence rates of ischemic stroke varied more than 3-fold by race and sex, the relationship between higher measures of obesity and ischemic stroke risk was positive and linear across all groups. The crude incidence of ischemic stroke was 1.2 per 1000 person-years for white women with the lowest body mass index, ranging up to 8.0 per 1000 person-years for black men with the highest body mass index. Hazard ratios for the highest versus lowest quintile of body mass index, waist circumference, and waist-to-hip ratio ranged from 1.43 to 3.19, indicating increased stroke risk associated with obesity, however it was measured, even after adjustment for potential confounders. Additional adjustment for factors that may mediate the relationship, such as diabetes and hypertension, significantly attenuated the associations, suggesting that these factors may explain much of the stroke risk associated with obesity.

Conclusions: Degree of obesity, defined by body mass index, waist circumference, or waist-to-hip ratio, was a significant risk factor for ischemic stroke regardless of sex or race.

Figure 1

Hazard ratio of ischemic stroke in relation to body mass index (a: black women, b: white women, c: black men, d: white men), and in relation to waist circumference (e: black women, f: white women, g: black men, h: white men) by cubic spline regression analysis, ARIC The solid line represents the hazard ratio; dotted line, 95% confidence intervals. The reference values were set at 22 kg/m² (a, b, c, d), and at 88 cm in women and 102 cm in men (e, f, g, h). The hazard ratios (HRs) were adjusted for age, education, smoking status, pack years, usual ethanol consumption, and physical activity. The sample for the spline analysis was truncated at the 1st and 99th percentile of body mass index.