Genetic Risk for Alzheimer Disease, Midlife Hypertension, and Dementia

BACKGROUND AND OBJECTIVES: Genetics represent a nonmodifiable risk factor for Alzheimer disease (AD), with 60%-80% heritability. Midlife hypertension is a modifiable risk factor for both dementia and death. Our primary objective was to determine how genetic risk for AD modifies the association between hypertension and dementia. METHODS: The Atherosclerosis Risk in Communities Study is an ongoing community-based prospective cohort study of 4 US centers. We analyzed White and Black participants free of dementia at age 55 years with genotypes and blood pressure measured at visit 1 (1987-1989). Three genetic risk groups (low, medium, high) were defined based on tertiles of a race-specific AD polygenic risk score. Dementia was ascertained through cognitive testing, informant interviews, hospitalization, codes and death records. Death was ascertained through the National Death Index. We examined the association of midlife hypertension with incident dementia within 3 genetic risk groups using Cox proportional-hazards and cumulative incidence function estimations. We used age 55 years as the time origin, with left truncation to allow entry at ages older than 55 years; age on December 31, 2022, was the administrative censoring date. RESULTS: Among 8,931 White and 2,666 Black participants, the median follow up time was 26.6 and 23.8 years, the mean age was 54.0/53.5 years, and 53.0%/62.5% were female, respectively. After adjusting for demographics, midlife hypertension was significantly associated with dementia incidence across all genetic risk groups among White participants (low risk hazard ratio [HR] 1.29; 95% CI 1.07-1.55, medium risk HR 1.34; 95% CI 1.13-1.58, high risk HR 1.19; 95% CI 1.03-1.38) and among Black participants at high genetic risk (HR 1.31; 95% CI 1.04-1.66). Associations for low and medium genetic risk Black participants were consistent but not statistically significant. There were no significant differences in association of hypertension with dementia by AD genetic risk group. Individuals with hypertension had a 0%-2% higher probability of developing dementia by age 80 and a 6%-13% lower probability of dementia-free survival to age 80 years vs those without hypertension, across race and genetic risk groups. DISCUSSION: Genetic risk for AD does not modify the association between hypertension and dementia. These data support the fact that all individuals with hypertension are likely to benefit from antihypertensive treatment.