Key findings for journalists
- Asians had the highest levels of cerebral microbleeds, small areas of bleeding that increase risk of stroke.
- White populations showed higher metabolic risks overall, including higher cholesterol, blood pressure and body mass index.
- Black and Hispanic groups experienced substantially higher rates of diabetes, a major driver of CSVD-related brain injury.
- When Asian subgroups were compared:
- Chinese cohorts had the highest white matter damage and microbleed burden, placing them at elevated haemorrhagic stroke risk.
- Japanese participants showed a tendency toward lacunes, tiny brain infarcts linked to narrowing of blood vessels.
Korean cohorts displayed a strong relationship between blood pressure levels and white matter disease, even at relatively younger ages.
A major international study involving more than two million adults worldwide has revealed striking ethnic differences in the brain changes that contribute to stroke and dementia.
The research - a PROSPERO-registered systematic review and meta-analysis published in Alzheimer’s & Dementia - The Journal of the Alzheimer's Association - led by UNSW Sydney’s Centre for Healthy Brain Ageing (CHeBA), examined cerebral small vessel disease (CSVD) - a common but often silent condition affecting the brain’s smallest blood vessels and a major driver of cognitive decline and stroke.
Lead author and PhD student Nikita Keshena Husein said the team’s analysis of 159 MRI-based studies showed that CSVD does not affect all populations in the same way.
“What we found is that the pattern of brain vessel damage differs markedly across ethnic groups,” Ms Husein said. “These aren’t subtle differences - these are meaningful variations that influence who is most at risk of certain types of stroke and cognitive decline.”
According to Ms Husein, some of the clearest contrasts appeared when comparing Asian, White, Black and Hispanic populations.
“Across studies, Asian participants had the highest levels of cerebral microbleeds, which are tiny areas of bleeding that raise the risk of haemorrhagic stroke,” she said.
“Meanwhile, White populations tended to show a much higher burden of metabolic risk- things like elevated cholesterol, higher blood pressure and greater body mass index.”
“Black and Hispanic groups, on the other hand, had substantially higher rates of diabetes, which we know is a major contributor to CSVD-related brain injury.”
A deeper look within Asian populations
The study also conducted the largest comparison to date of Chinese, Japanese and Korean cohorts, revealing striking intra-Asian differences.
“Chinese groups showed the greatest burden of white matter damage and microbleeds,” said Ms Husein. “This profile places them at particularly high risk of haemorrhagic stroke.”
“Japanese participants displayed a very different pattern, with a tendency toward lacunes - small, deep brain infarcts caused by vessel narrowing. In contrast, Korean cohorts showed a strong link between blood pressure and white matter disease, even at younger ages, suggesting an accelerated vulnerability.”
Context strengthened by CHeBA-led COSMIC consortia
Associate Professor Wei Wen, senior author and Leader of CHeBA’s Neuroimaging Group, said the findings are strongly supported by global evidence from the Cohort Studies of Memory in an International Consortium (COSMIC), also led by CHeBA.
“COSMIC has shown for years that the same risk factor can have very different effects depending on the population,” Assoc Prof. Wen said. “For example, COSMIC demonstrated that high blood pressure is more strongly associated with white matter damage in White cohorts than in Asian ones.”
“Our new analysis reinforces this idea: genetics, environment and vascular health interact in ways that are deeply shaped by ethnicity and region.”
He added that COSMIC’s work on the APOE ε4 gene - differentially associated with cognitive decline across ethnicities - further highlights the complexity of these interactions.
Why these differences matter
The researchers emphasise that the findings challenge one-size-fits-all approaches to stroke and dementia prevention.
“The risks look different depending on who you are,” Ms Husein said. “For Chinese and other East Asian groups, earlier and stricter control of blood pressure, diabetes and even sodium intake may be critical. Japanese populations may particularly benefit from intensive blood pressure management to prevent lacunar stroke.”
“For White populations, comprehensive metabolic management is key. And for Black and Hispanic communities, better access to diabetes care and interventions that address broader health inequities could make a profound difference.”
A call for more diverse and inclusive research
A major limitation identified in the review was the lack of multi-ethnic cohorts: fewer than 1% of participants in the total sample were drawn from studies that included more than one ethnic group.
“We urgently need large, multi-ethnic cohorts where people of different backgrounds are studied side by side,” Assoc Prof. Wen said. “Without this, it becomes very difficult to disentangle biological differences from social or healthcare-related factors.”
He noted that global collaborations such as COSMIC and the ENIGMA consortium show how harmonised international data can reveal patterns that individual studies cannot.
Implications for clinicians and patients
The authors stress that clinicians should consider ethnicity-specific risk patterns when screening patients for stroke or dementia risk.
“Ultimately, our message is simple,” Ms Husein said. “CSVD is not the same disease in every population. Understanding these differences is essential if we want to deliver prevention strategies that actually work.”
Contact details:
Heidi Douglass