Racial disparities in stroke incidence in the Women's Health Initiative: Exploring biological, behavioral, psychosocial, and social risk factors

Background: - Disparities in incident stroke risk among women by race and ethnicity persist. Few studies report the distribution and association of stroke risk factors by age group among a diverse sample of women. Methods: - Data from the Women's Health Initiative (WHI) Observational Study collected between 1993 and 2010 were used to calculate cumulative stroke incidence and incidence rates among non-Hispanic African American (NHAA), non-Hispanic white (NHW), and Hispanic white or African American (HWAA) women by age group in participants aged ≥50 years at baseline (N = 77,247). Hazard ratios (HRs) and 95% CIs for biological, behavioral, psychosocial, and socioeconomic factors overall and by race or ethnicity were estimated using sequential Cox proportional hazard regression models. Results: - Average follow-up time was 11.52 (SD, 3.48) years. The incident stroke rate was higher among NHAA (306 per 100,000 person-years) compared to NHW (279/100,000py) and HWAA women (147/100,000py) overall and in each age group. The disparity was largest at ages >75 years. The association between stroke risk factors (e.g., smoking, BMI, physical activity) and incident stroke varied across race and ethnicity groups. Higher social support was significantly associated with decreased stroke risk overall (HR:0.84, 95% CI, 0.76, 0.93); the degree of protection varied across race and ethnicity groups. Socioeconomic factors did not contribute additional stroke risk beyond risk conferred by traditional and psychosocial factors. Conclusions: - The distribution and association of stroke risk factors differed between NHAA and NHW women. There is a clear need for stroke prevention strategies that address factors driving racial disparities in stroke risk.