White women—but not black women—between the ages of 65 and 74 carried a lower risk of stroke than their male counterparts in a U.S. study, suggesting gender-specific protections against stroke vanish earlier among blacks.
Published online Dec. 10 in JAMA Neurology, the study included 25,789 black and white participants from the Reasons for Geographic and Racial Differences in Stroke (REGARDS) cohort. Over a follow-up period ranging from nine to 13 years, it was found that women of both races between the ages of 45 and 64 had significantly lower rates of stroke than men—white women had a 32 percent lower stroke risk than white men and black women had a 28 percent lower risk than black men.
The sex differences in stroke risk for both races appeared to level off after 75 years of age, but in the 65- to 74-year-old range, only white women maintained a lower stroke risk than their male counterparts. Their risk was reduced by 29 percent, while black women were at a statistically insignificant 6 percent lower odds of suffering stroke compared to black men.
“Others have reported women are at lower stroke risk than men through age 75 years, with equivalent or higher stroke risk at older ages, based on data primarily from white populations,” wrote Virginia J. Howard, PhD, with the School of Public Health at the University of Alabama at Birmingham, and colleagues. “However, among black participants in the REGARDS study, we found that the lower ischemic stroke rate in women dissipated at the earlier ages of 65 through 74 years old, with little difference in the stroke risk between women and men.
“While primordial and primary stroke prevention efforts are important to all individuals, a greater emphasis on these efforts at younger ages in black women may have a larger return.”
Previous reports have found that black individuals are at about triple the risk of stroke compared to whites between 45 and 64 years old, with those differences declining later in life and being undetectable after the age of 85. However, they didn’t look at sex disparities in stroke rates among these racial groups, according to Howard et al.
The authors also analyzed the association of various risk factors with the likelihood of suffering stroke among subgroups. They determined there was little evidence of sex-specific differences for any risk factors among black participants. However, multiple variables were linked more strongly to stroke risk for white women versus white men, including:
- Systolic blood pressure—Hazard ratio (HR): 1.13 in women, 1.04 in men
- Diabetes—HR: 1.84 in women, 1.13 in men
- Heart disease—HR: 1.76 in women, 1.26 in men
“It is unexplained why we observed differential effects of risk factors by sex in white individuals but not black individuals,” the researchers wrote. “It could be an issue of statistical power for factors such as diabetes, for which there was no association with incident stroke among black individuals. We also speculate that there may be racial differences in the severity and/or extent of control of risk factors that were not accounted for in our models but could affect stroke risk differentially by race.”
Given this information, Howard and colleagues suggested clinicians pay particular attention to factors like diabetes and a history of heart disease among white women to reduce their stroke risk.
“While prevention and management of these risk factors is important across all racial/ethnic and sex groups, sex-specific approaches may be warranted in white individuals,” they wrote.