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Middle-aged Black Americans with comorbid hypertension and diabetes may face increased risk for neurodegeneration, according to a recently published study.

Middle-aged Black Americans with comorbid hypertension and diabetes may face an increased risk for neurodegeneration, according to findings published in The Journal of Racial and Ethnic Health Disparities.

The study found that, over an 11-year period, hypertension and diabetes comorbidity was associated with higher levels of serum neurofilament light chain (NfL), a non-specific marker of neurodegeneration, but not the Alzheimer disease (AD) biomarker phosphorylated tau181 (p-Tau181).

“Rather than being instances of AD, elevated rates of dementia among Black Americans may be largely vascular pathology caused by high rates of diabetes and high blood pressure,” wrote study author Michelle M. Mielke, PhD, Wake Forest University, and coauthors.

Vascular Burden & Dementia Risk

According to the authors, evidence suggests an increased risk for AD and related dementias among Black Americans compared with non-Hispanic White Americans, however, mechanisms behind the increased risk are not well understood. The researchers investigated whether an elevated risk for vascular pathologies such as hypertension and diabetes in Black Americans could help explain early neurodegeneration observed in this population.

Using data from the Family and Community Health Study, researchers analyzed the records of 252 Black Americans from Iowa and Georgia, ranging in age from 45 to 79 years, with diagnoses of hypertension and diabetes recorded in 2008. Blood samples from both 2008 and 2019 were analyzed for NfL and p-Tau181 levels.

Neurodegeneration Without Alzheimer-Specific Biomarkers

Results showed that having either hypertension or diabetes alone in middle age did not affect levels of NfL or p-Tau181. However, participants with both conditions had significantly elevated NfL in 2019 and a significant increase in NfL over the 11-year period, compared with those who had neither diagnosis.

“Neither a diagnosis of hypertension, diabetes, nor being comorbid for both was associated with p-Tau181 level in 2019 or increase in p-Tau181 level between 2008 and 2019,” the researchers reported

The findings suggest that vascular pathologies, and not necessarily a predisposition to AD, may be behind earlier cognitive decline in many Black Americans.

Implications for Prevention

“The current study supports prior research showing that comorbid diabetes and hypertension exacerbate neurodegeneration and negatively impact brain health,” the researchers wrote. “These results highlight the importance of addressing vascular risk factors early to reduce their long-term consequences on brain aging.”