PROJECT SUMMARY – PROJECT 1 The population of Americans with Alzheimer’s Disease and related dementia (ADRD) is expected to triple by 2050. There is great hope for new treatment options, but currently we are limited to managing established disease and avoiding further negative outcomes. While no breakthrough treatments have emerged, the last 20 years have seen large changes in the diagnosis and management of ADRD with the introduction of the first symptomatic drugs and advanced diagnostic technologies, such as amyloid positron emission tomography (PET) scanning and cerebrospinal fluid biomarkers. Whether early diagnosis is helpful is unknown and controversial, as evidenced by national guidelines that disagree on whether to screen for ADRD. The mixed messages likely contribute to wide differences in observed state-specific prevalence of clinically diagnosed ADRD from what would be expected based on epidemiological estimates, ranging from 30% below to 10% above the expected prevalence. Such differences in ascertainment of disease suggest that the process of getting a clinical diagnosis of ADRD varies across health systems. Using this variation across health systems and changes over time, we propose to gain insights into how diagnostic intensity and early diagnosis relate to clinical outcomes of hospitalization, pharmaceutical use, and end-of-life care among elderly populations in the U.S. We will use national Medicare administrative data linked to nursing home data, the Health & Retirement Study from 1996-2018 and the Nurse’s Health Study from 1995-2018. Our underlying hypothesis is that in some regions, people are both more likely to receive a diagnosis of ADRD and more likely to be diagnosed early. We will use these quasi-experimental variations in the extent and timing of diagnosis across regions and over time to assess the value of early diagnosis on subsequent treatments and clinical outcomes.