Comparing characteristics among ADRC cohorts stratified by percentage of autopsied cases that were normal versus demented at visit prior to death

Abstract Background Dementia‐enriched research studies and normal control‐enriched research studies have different recruitment models and thus may differ in clinical and demographic characteristics. These distinctions can contribute to different study findings and perspectives. We generated a novel operationalization for cohort status in NIA‐funded Alzheimer’s Disease Research Centers (ADRC), based on the proportion of research participants that were normal, or demented, prior to death. Based on that operationalization, we compared differences in the rates of several clinical features among participants who came to autopsy. Method Data were obtained from the National Alzheimer’s Coordinating Center (NACC). Eligibility criteria included participants with autopsy data available and ADRCs with > = 30 eligible participants. 31 different ADRC autopsy cohorts were thus included, and the total number of individual research participants was 6,722. The first 3 digits of participant zip codes were included in the study. ADRCs were assigned to two groups based on the proportion of participants with normal cognition to participants with dementia. The “more non‐demented “(MN; n = 18) group included ADRCs with >10% ratio of normal to dementia participants, while the “more dementia” (MD; n = 13) group included ADRCs with <10% ratio of normal to dementia participants. Clinical features and diagnoses were compared between the two groups using Pearson’s chi‐square for the categorical variables and two‐sample t‐tests for the continuous variables. Result The overall cohort sizes were similar between groups and clinical Alzheimer’s disease (AD) was diagnosed at similar rates in both MN and MD ADRCs. MD ADRCs had more frontotemporal lobar degeneration (FTLD) and Lewy body disease (LBD) diagnoses than MN centers, while MN centers had more cerebrovascular disease and participants were on average older at death than those in MD ADRCs. Other trends identified were that MN ADRCs had lower rates of APOEɛ4 and MD ADRCs tended to include cases from a larger number of different zip codes. Conclusion In this sample, we found differences in clinical features between MD and MN ADRCs that probably reflect study designs related to recruitment practices. Future research examining additional features may yield further elaborate discrepancies found between these types of autopsy cohorts.