At the age of 45, black people have a 2.7 times higher risk of a first stroke than white people of the same age, reported investigators of a longitudinal, population-based study published in Neurology. This disparity by race diminishes with advancing age until it disappears fully by age 85, when first-time stroke risk is similar for both races.
These results came from a study of 29 682 black and white participants (aged 45 and older) from the Reasons for Geographic and Racial Differences in Stroke (REGARDS) trial who were followed for an average of 6.8 years. The majority of the participants (90%) had not experienced a stroke or transient ischemic attack (TIA) at baseline, while the remaining 10% (n = 2993) had. Of those who had had a prior event, 301 people had a second stroke, while another 818 people experienced a first stroke during the study period.
More significantly, black and white individuals demonstrated similar risks for a second stroke, suggesting a different pattern by race that equalized by age 85. “The interaction between black race and age appears to be remarkably different for the risk of first versus second stroke,” explained lead author George Howard, DrPH, professor and chair of Biostatistics at the University of Alabama at Birmingham, Alabama. “There was very little difference in race for the risk of a second stroke,” he observed, although the pattern of risk from a first stroke to a second stroke did vary by race. The study found a substantially higher risk of a second stroke in white individuals who had a first stroke or TIA by the age of 45 (HR = 14.2) compared to black individuals who had a first stroke or TIA by the age of 45 (HR = 5.7).
This divergence in risk rates did not indicate an actual higher risk of second stroke in white individuals, but represented a convergence of the risk rates for both races associated with age. Among white study participants, the risk of a second stroke went from 14.2 times higher risk at age 45 to 1.81 times increased risk by age 85. The difference in risk rates was much smaller among blacks due to the substantially higher incidence of first strokes at baseline, and so the risk of a second stroke went from 5.8 times higher risk at age 45 to 1.48 times higher risk at age 85.
Known risk factors for first stroke, including hypertension, diabetes, current smoking, atrial fibrillation, left ventricular hypertrophy, heart disease, and male sex all had only a slightly smaller influence on the risk of a second stroke. “Almost all of the ‘traditional’ risk factors for a first stroke proved to also be a risk factor for a second stroke, suggesting that controlling these risk factors may help avoid both conditions,” Dr. Howard reported.
Howard G, Kissela BM, Kleindorfer DO, et al. Differences in the role of black race and stroke risk factors for first vs recurrent stroke. Neurology. February 16, 2016.