A non-APOE polygenic score for Alzheimer's disease and APOE-ε4 have independent associations with dementia in the Health and Retirement Study

INTRODUCTIONAlzheimers disease (AD) is a common and costly neurodegenerative disorder. A large proportion of risk is heritable and many genetic risk factors for AD have been identified. The cumulative genetic risk of known markers has not been benchmarked for dementia in a population-based sample. METHODSIn the United States population-based Health and Retirement Study (HRS) (waves 1995-2014), we evaluated the role of cumulative genetic risk for AD, with and without the APOE-{varepsilon}4 alleles, on dementia status (dementia, cognitive impairment without dementia, borderline cognitive impairment without dementia, cognitively normal). We used logistic regression, accounting for demographic covariates and genetic principal components, and analyses were stratified by European and African genetic ancestry. RESULTSIn the European ancestry sample (n=8399), both AD polygenic score excluding the APOE genetic region (odds ratio (OR)=1.10; 95% confidence interval (CI): 1.00, 1.20) and the presence of any APOE-{varepsilon}4 alleles (OR=2.42; 95% CI: 1.99, 2.95) were associated with the odds of dementia relative to normal cognition in a mutually-adjusted model. In the African ancestry sample (n=1605), the presence of any APOE-{varepsilon}4 alleles was associated with 1.77 (95% CI: 1.20, 2.61) times higher odds of dementia, while the AD polygenic score excluding the APOE genetic region was not significantly associated with the odds of dementia relative to normal cognition 1.06 (95% CI: 0.97, 1.30). DISCUSSIONCumulative genetic risk for AD and APOE-{varepsilon}4 are both independent predictors of dementia. This study provides important insight into the polygenic nature of dementia and demonstrates the utility of polygenic scores in dementia research.