Black men are most likely to suffer from intracranial atherosclerotic disease (ICAD), an important contributor to stroke, while midlife risk factors for the illness vary between blacks and whites, according to a new study published in JAMA Cardiology.

It’s known that strokes are reported more often in black patients than in white patients, first author Ye Qiao, PhD, and colleagues wrote, but research hasn’t yet determined if ICAD is also more prevalent in the black population. Recent technological advances have made ICAD identification and characterization more accurate—especially 3D vessel wall MRIs, which allow clinicians to take more reliable intracranial vessel wall measurements—but older studies of ICAD and its risk factors are outdated.

Qiao and colleagues drew 1,752 participants from the Atherosclerosis Risk in Communities (ARIC) study, a community-based, prospective investigation of nearly 16,000 black and white individuals between 45 and 64 years old. All participants hailed from four counties in North Carolina, Mississippi, Minnesota and Maryland, according to the study, and few had histories of stroke.

The patients, who were initially recruited for ARIC in the 80s, underwent 3D intracranial vessel wall MRI testing between 2011 and 2013, Qiao and co-authors wrote, and were measured for intracranial plaque presence, size and number. At the time of Qiao’s study, participants were an average of 78 years old, and the majority—nearly 70 percent—were white.

The researchers found black patients exhibited the highest prevalence of ICAD, at 50.9 percent of men and 35.9 percent of women. White men had 35.5 percent prevalence, and white women had the lowest number, at 30.2 percent. Black men also had the highest frequency of multiple plaques, Qiao et al. reported, at 22.4 percent, compared to the lowest prevalence in white women: 8.7 percent.

Prevalence of the disease seemed to increase with age, the authors noted, reaching 50 percent before ages 68, 84 and 88 in black men, white men and white women, respectively. Midlife hypertension and hyperlipidemia were significant risk factors for ICAD, increasing in prevalence by 29 percent and 18 percent, respectively, across all groups.

Qiao and colleagues found that risk factors differed between races—midlife smoking and diabetes were strongly correlated with late-life ICAD in blacks, but not whites, while midlife hypertension and hyperlipidemia were connected to late-life ICAD in both races.

“Identifying these midlife risk factors and understanding their implications based on race and sex is an important step in preventive treatment strategies, recognizing that the effect of these strategies may not be perceived for decades,” the authors wrote.

They said the results of this first-ever study could add to the expanding knowledge of, and explanations for, stroke rates in the U.S.

“Racial differences in intracranial atherosclerotic disease prevalence may help to explain stroke rates in the United States, and differences in ICAD risk factors could offer insight into preventive risk-factor management strategies,” they wrote.