P3‐556: NEUROPATHOLOGICAL DIFFERENCES ACROSS THREE ETHNORACIAL GROUPS WITH DEMENTIA

Recent studies have found differences in neuropathologic diagnoses between Black and non-Hispanic White participants with clinical Alzheimer's disease (AD). Being able to better understand and identify underlying pathology of individuals with clinical dementia is crucial for either prevention or targeted treatments for dementia. Understanding the role that race/ethnicity plays in the etiology of dementia is similarly critical for future public health policies. Objective: To compare the occurrence of mixed neuropathology diagnoses to that of solely Alzheimer's disease (pure-AD) in Black, non-Hispanic White, and Hispanic participants with clinical dementia. Pure-AD was defined as AD being the leading, single dementia pathology found in the autopsied brain, while mixed referred to a brain having multiple neuropathological diagnoses. Participants included 751 persons enrolled in the UC Davis Alzheimer's Disease Center. We examined neuropathological diagnoses of 35 Black, 28 Hispanic, and 688 non-Hispanic White decedents. Given the comparatively small number of minority subjects, we used a bootstrap procedure along with logistic regression standardization to project pure-AD rates for non-Hispanic whites to the characteristics of the minority samples, adjusting for relevant covariates. Pure-AD was confirmed in 14 of 35 Black (40%), 6 of 28 Hispanic (∼21%) and 348 of 688 (∼51%) non-Hispanic White participants. Bootstrap sampling and logistic regression in non-Hispanic Whites predicted a pure-AD pathology in Blacks averaging 48%, 95% bounds [41%-56%]). The observed value of 40% was lower, but consistent with binomial chance variation (mean two-sided p value = 0.41). More dramatically, the observed proportion of pure-AD for Hispanic individuals at 21% was well below the range of predictions (mean = 50%, 95% bounds [41%-61%]). The mean two-sided p value was 0.008. Similar analyses were done with plaque and tangle scores used to confirm diagnosis.