Project Summary / Abstract The overarching goal of this project is to develop the evidence base around the predictors and consequences of clinical underdiagnosis vs early clinical diagnosis of Alzheimer’s disease and related dementias (ADRD) in healthcare settings. Many older persons who would meet diagnostic criteria for dementia—potentially more than half—are underdiagnosed in the healthcare setting, meaning they are diagnosed by their provider years after symptoms that meet criteria for dementia first emerge (i.e. late diagnosis) or are never diagnosed (i.e. missed diagnosis). We know relatively little about the factors that drive the timing of receipt of a clinical diagnosis of dementia. Advances in this area would allow us to address diagnostic disparities. In recent years, there has also been a push for early clinical diagnosis of dementia (i.e. identifying persons with dementia close to the time of symptom onset), despite lack of an effective disease-altering treatment for ADRD. The importance of an early clinical dementia diagnosis would be bolstered by clear evidence that it led to better long-term health for diagnosed patients, more appropriate healthcare utilization, or decreased medical costs. Conversely, evidence of harms would suggest a renewed focus on improving dementia care is warranted. However, the benefits and harms related to the timing of a clinical dementia diagnosis remain poorly characterized. This project will address these crucial gaps in understanding by leveraging unique data from 5 diverse, harmonized cohorts of aging from the Rush Alzheimer’s Disease Center (RADC) with robust cognitive assessment and linked Medicare claims records from 1991 to the present. This data is perfectly suited to these aims, as study-based dementia ascertainment is frequent (annual) and classification of dementia is not disclosed to participants—thus it is independent of clinical diagnosis in healthcare settings captured in the Medicare claims. We propose to characterize the factors that make older adults with dementia more or less likely to receive a clinical diagnosis around the time when they first meet criteria for ADRD (Aim 1), and to test whether those with early diagnosis have better health outcomes (Aim 2), and more appropriate healthcare utilization and less associated costs (Aim 3). These efforts are timely and have the potential to change public perception, clinical practice, and health policy. Patients and medical providers will be able to make better informed choices about when to seek or offer cognitive evaluation, while public health agencies, health systems, and health insurers will be able to use our findings to decide whether and how to promote early cognitive evaluation and diagnosis of dementia.