Diabetes, hyperglycemia, and brain MRI biomarkers: results from SOL-INCA MRI study

OBJECTIVE: Hispanic/Latino individuals have higher rates of type 2 diabetes and Alzheimer's Disease and Related Dementia (ADRD) burden compared to non-Hispanic whites. Diabetes is a risk factor for ADRD, but the extent of its associations with brain markers in community-dwelling Hispanic/Latino individuals is unknown. We examined how glycemic dysregulation and diabetes associate with small vessel disease damage and neurodegeneration in Hispanic/Latino adults from a large and community-representative cohort study. RESEARCH DESIGN AND METHODS: We used data from 2627 individuals, aged 35-85 years, from the Hispanic Community Health Study/Study of Latinos (HCHS/SOL; 2008-2011) who underwent brain imaging through the SOL/Investigations of Neurocognitive Aging MRI (SOL-INCA MRI; 2018-2022) study. Exposures included diabetes status and HbA1c (%) levels. Outcomes included white matter hyperintensities, free water, fractional anisotropy, and volumetric regions including hippocampus, lateral ventricles, total brain, and cortical gray matter. RESULTS: Diabetes status, compared to no diabetes, was associated with larger white matter hyperintensity volume, lower fractional anisotropy, and higher free water. Diabetes status was also associated with larger lateral ventricles as well as smaller total brain, frontal gray matter, and occipital gray matter volumes. The association between diabetes and brain MRI outcomes was stronger in middle-aged and older individuals (50 years and older) compared to younger individuals (35-49 years). CONCLUSION: Diabetes was associated with markers of small vessel disease (white matter micro and macrostructural damage) and neurodegeneration (smaller brain volumes). White matter hyperintensities have been associated with increased risk of stroke and cognitive decline. Other work has found that free water and fractional anisotropy may predict worse cognitive performance, even in normal-appearing white matter. Smaller brain volumes have also been associated with cognitive deficits. These findings highlight the additional ADRD burden this population faces due to their higher diabetes prevalence.