Associations of Alzheimer Disease and Related Dementia Neuropathologies With Timely Diagnosis of Dementia in Healthcare Settings

BACKGROUND AND OBJECTIVES: A timely diagnosis of dementia may provide valuable time for treatment and planning, yet underdiagnosis is common. This study investigated the relationship between presence of dementia pathologies and timeliness of dementia diagnosis by healthcare providers. METHODS: This was a retrospective study using 5 cohorts at Rush Alzheimer's Disease Center. We included participants who met all of the following criteria: (1) incident dementia based on annual cohort assessments, (2) linkage to Medicare records, and (3) a completed postmortem brain autopsy. Postmortem neuropathologic examinations identified the presence of AD, limbic-predominant age-related TDP-43 encephalopathy neuropathologic change (LATE-NC), vascular pathologies, and neocortical Lewy bodies (LBs). In linked Medicare data, we defined timely diagnosis as the presence of claims with dementia diagnoses within 3 years before or 1 year after the cohort-based dementia onset. We used logistic regressions to quantify associations of neuropathology markers with timely diagnosis vs underdiagnosis. RESULTS: Of the 500 eligible participants (71% female, 95% non-Latino White, mean [SD] age at cohort dementia onset = 88 [7] years, mean [SD] years from onset to death = 4 [3]), only 54% received a timely diagnosis. After controlling for demographics, time to death, and other neuropathologies, a pathologic diagnosis of AD (OR = 1.91, 95% CI 1.21-3.00) and moderate/severe LATE-NC pathologies (OR = 1.83, 95% CI 1.25-2.68) were independently associated with higher odds of timely diagnosis. Moderate/severe vascular pathologies (OR = 0.94, 95% CI 0.55-1.59) and neocortical LB pathologies (OR = 1.00, 95% CI 0.64-1.55) were not significantly associated with receipt of a timely diagnosis. In a separate multivariable logistic regression, we found that participants with 3 or 4 neuropathologies present had an over 2-fold increase in odds of timely diagnosis (OR = 2.24, 95% CI 1.32-3.82), compared with those with 1 or no neuropathology. DISCUSSION: In deceased older adults with cohort-determined incident dementia, the healthcare system was twice as likely to capture those with pathologic diagnosis of AD, moderate/severe LATE-NC, and more than 3 copathologies in a timely manner. While findings from this predominantly White and highly educated sample warrant replication in broader population, this study is an important initial step toward understanding biological correlates of timely diagnosis of dementia.