Racial Differences in the Association between Parity and Incident Stroke: Results from the REasons for Geographic and...

Circulatory and vascular changes across consecutive pregnancies may increase the risk of later-life cerebrovascular health outcomes.

The association between parity and incident stroke was assessed among 7674 white and 6280 black women, aged 45 years and older, and enrolled in the REasons for Geographic and Racial Differences in Stroke Study from 2003 to 2007. Parity was assessed at baseline, and incident stroke was ascertained from physician-adjudicated medical records through September 2014. Cox proportional hazards models were used to estimate hazard ratios (HR) for the association between parity and stroke, adjusting for baseline measures.

At baseline, 12.7% of white women and 16.2% of black women reported 1 live birth, while 8.2% and 19.0%, respectively, reported 5 or more live births. Mean follow-up time was 7.5 years (standard deviation = 2.8); there were 447 incident strokes. A significant interaction between race and parity was detected (P = .05). Among white women, those with 5 or more live births had a higher stroke risk than those with 1 live birth (HR = 1.57; 95% confidence interval [CI] .93-2.65). However, the association was eliminated after adjustment for baseline characteristics (HR = 1.00, 95% CI .59-1.71). For black women, those with 5 or more live births had the highest stroke risk compared with those with 1 live birth (HR = 1.91, 95% CI 1.25-2.93), but the association was attenuated and no longer statistically significant after adjustment for confounders (HR = 1.40, 95% CI .89-2.18).

In adjusted models, no statistically significantassociations were observed between parity and stroke risk in a diverse cohort of U.S. women. Further studies are needed to elucidate the role of lifestyle and psychosocial factors in the race-specific associations that were observed.