Black women in their late 60s and early 70s had the same stroke risk as black men, unlike patterns found among white men and women, researchers reported.
From ages 45 to 74, white women were less likely than white men to have an ischemic stroke, but black women had a lower stroke risk than black men only until age 64, reported Virginia Howard, PhD, of the University of Alabama at Birmingham, and colleagues in JAMA Neurology.
“It was already known that women have a greater protection from stroke at younger ages, but women have relatively similar stroke risk as men at the oldest ages,” said Howard. “What was not known was whether this age pattern of stroke risk was the same for blacks and whites.”
“Our work suggests that the men-to-women stroke risk may be different by race for the age group 65 to 74 years: for blacks in this age group, the lower stroke risk in women compared to men was not evident, while it remained lower in whites,” Howard told MedPage Today.
In the U.S., the largest racial disparity in stroke risk is between black and white individuals. From ages 45 to 64, black individuals have a three-fold higher risk of stroke than white individuals, but these differences fade by age 85.
In this study, Howard and colleagues studied 25,789 participants ages ≥45 from the national REGARDS (Reasons for Geographic and Racial Differences in Stroke) cohort. Stroke-free participants enrolled from 2003 through 2007 and were followed until October 2016; 54.9% were female and 39.9% were black. Black individuals and residents of the southeastern U.S. were over-sampled in this study.
Compared with white individuals, black individuals of both sexes had lower socioeconomic status and a generally worse risk factor profile than white individuals: they had higher systolic blood pressure levels and were more likely to be taking anti-hypertensive medications. The prevalence of diabetes was approximately twice as high for black participants than white participants.
Over the follow-up period, 939 ischemic strokes occurred: 159 in black men, 326 in white men, 217 in black women, and 237 in white women. Crude stroke incident rates showed:
- From ages 45 to 64, white women had 32% lower stroke risk than white men (IRR 0.68, 95% CI 0.49-0.94), and black women had a 28% lower risk than black men (IRR 0.72, 95% CI 0.52-0.99)
- From ages 65 to 74, lower stroke risk in women versus men persisted in white individuals (IRR 0.71, 95% CI 0.55-0.94), but not in black individuals (IRR, 0.94, 95% CI 0.68-1.30); the race-sex interaction was not significant
- At ages ≥75, there was no sex difference in stroke risk for either race
In a fully adjusted model, there was no evidence of a sex difference for any risk factors among black individuals. But among white participants, diabetes, higher systolic blood pressure, and history of heart disease increased stroke risk more for women than men, while using anti-hypertensive medications was tied to a lower stroke risk in women.
“For individuals between 65 and 74, there is a suggestion that sex differences may only be present in whites: white women ages 65 to 74 years have fewer strokes than do white men in that age group, but among black participants aged 65 to 74, stroke races are similar in men and women. The investigators did not actually find evidence of a significant interaction by sex and race, so we have to be cautious in the interpretation of the results,” observed Rebecca Gottesman, MD, PhD, of Johns Hopkins University in Baltimore, who was not involved with the study.
Although the researchers adjusted for many factors by which the four race-sex groups differ, “they are so different in many ways that it’s likely there are continued other ways in which these groups differ,” Gottesman told MedPage Today. “Therefore, it is hard to know for sure if this suggestion of a difference in sex disparities among blacks between 65 and 74 years old is truly due to a different pattern by race or is simply driven by differences in underlying risk factors.”
“From the actual stroke event numbers, it looks as though the relative lack of difference in stroke rates between black men and women between 65- and 74-years-old is driven by increased rates of stroke in black women, rather than lower rates in black men,” she added. “Stroke prevention strategies should consider the increased risk in some of these groups.”
Howard’s group reported several limitations to the study. Participants may not be representative of the general population, and some data may have been misclassified. The study was observational and causal inferences cannot be drawn. Not all medical records for suspected stroke could be obtained, they added, but multiple imputation methods helped address this.
The REGARDS project is supported by the National Institute of Neurological Disorders and Stroke and the National Institute on Aging.
The study was supported by the National Heart, Lung, and Blood Institute.
Howard disclosed no relevant relationships with industry. Co-authors disclosed relevant relationships with Janssen and AbbVie.