Influence of Cardiometabolic and Alzheimer Disease Genetics on Cognitive-Related Outcomes in a Diverse Population

Late-life dementia has a strong heritable component. While the APOE ɛ4 allele is the strongest genetic risk factor of Alzheimer disease (AD), polygenic risk factors also play a significant role. Cardiometabolic diseases (CMDs) and their risk factors predict dementia in many cohorts, but how genetic predictors of CMD influence dementia-related outcomes remains unclear. In this study, we examined the associations of polygenic risk scores (PRSs) for major CMDs and the established APOE risk alleles with dementia-related outcomes in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study, which is enriched for Black participants underrepresented in late-life dementia research.

We constructed PRSs for AD and related dementias (ADRDs) and CMDs, including stroke, coronary artery disease, venous thromboembolism, type 2 diabetes, atrial fibrillation, blood pressure (systolic blood pressure, diastolic blood pressure, and pulse pressure), and circulating lipid levels (high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglycerides), using lead genome-wide significant genetic variants from the latest genome-wide association studies. We evaluated the predictive performance of each PRS on their primary end point and tested their associations with incident cognitive impairment (ICI), assessed using the 6-item screener and enhanced cognitive battery, and dementia as a contributing cause of death (DCCD). In addition, we explored the impact of APOE variants and, based on previous reports, local genetic ancestry at the APOE locus on these dementia-related outcomes.

Up to 8,818 participants were analyzed (mean age 63.7 years; 58.9% female; 83.3% Black). For CMD PRS, we identified a significant association between PRS for pulse pressure and DCCD (hazard ratio [HR] 1.16, 95% CI 1.06-1.28, p < 1.76 × 10^-3). We observed that the PRS for ADRD was associated nominally with DCCD (HR 1.12, 95% CI 1.00-1.25), but not with ICI among REGARDS participants, suggesting heterogeneity in associations across different cognitive-related end points. Furthermore, we identified a nominally significant (p < 0.1) attenuated effect of APOE risk alleles on ICI among those with African ancestry at the APOE locus, similar to previous reports.

Higher PRS for pulse pressure was associated with increased DCCD risk, supporting shared genetic underpinnings between CMD and dementia.