Abstract P173: Racial Differences in the Association Between Parity and Incident Stroke: The REasons for Geographic and Racial Differences in Stroke (REGARDS) Study

Background: Circulatory and vascular changes occurring during pregnancy may increase the risk of adverse cerebrovascular health outcomes in later life. Previous studies have examined the association between parity and stroke, but the results have been inconsistent. No studies have examined racial differences in this association. Hypothesis: We assessed the hypothesis that higher parity is associated with an increased risk of stroke and that this association varies by race in a large and diverse cohort of U.S. women. Methods: The association between parity and incident stroke was assessed among 8339 white and 7037 black women, aged 45 years and older, without a history of stroke who enrolled in the REasons for Geographic and Racial Differences in Stroke (REGARDS) Study between 2003 and 2007. Parity was assessed at baseline and stroke cases were ascertained through biannual follow-up interviews and adjudicated with medical records through September 2013. Cox proportional hazards models were used to estimate hazard ratios (HR) for the association between parity and stroke, adjusting for baseline measures, including sociodemographics (age, race, education, marital status, income, region), behavioral characteristics (smoking, alcohol), reproductive history (menopause, oral contraceptive use, hormone replacement therapy), and stroke risk factors (history of hypertension, diabetes, and heart disease). Results: At baseline, 12.8% of white women and 16.2% of black women reported one prior live birth, while 8.1% and 19.0%, respectively, reported five or more prior live births. The mean follow-up time for all women was 6.9 years (SD=2.5) and there were 457 incident stroke cases (388 ischemic, 34 hemorrhagic, and 35 unknown stroke types). A significant interaction between race and parity was detected (p=0.05). Among white women, those with five or more live births had a higher risk of stroke than those with only one prior live birth (HR=1.3, 95% CI 0.8, 2.3), but the association was attenuated after adjustment for stroke risk factors and sociodemographic, behavioral, and reproductive characteristics (HR=0.9, 95% CI 0.5, 1.6). For black women, those with five or more live births had the highest risk of stroke as compared to those with only one prior live birth (HR=1.8, 95% CI 1.2, 2.8), but the association was attenuated and no longer statistically significant after adjustment for confounders (HR=1.5, 95% CI 0.9, 2.4). Conclusion: There were no statistically significant associations observed between higher parity and the risk of stroke in a diverse cohort of U.S. women. Further analyses are needed to elucidate the role of biological, lifestyle, and psychosocial factors in the race-specific associations that were observed.