Undiagnosed dementia and mortality among older adults in the United States and Brazil: A cross-national cohort study.

INTRODUCTION

Cross-national evidence on undiagnosed dementia and its prognostic implications remains limited. We compared the proportion of undiagnosed dementia, associated factors, and mortality in the United States and Brazil.

METHODS

This population-based cohort study included adults aged ≥ 65 years from the 2016 US Health and Retirement Study (n = 9,539) and the 2015-2016 Brazilian Longitudinal Study of Aging (n = 3603), followed for mortality through 2020. Dementia was classified as no dementia, undiagnosed dementia, or diagnosed dementia using harmonized cognitive, functional, and informant measures.

RESULTS

The proportion of undiagnosed dementia was higher in Brazil (76.1%) than in the United States (45.1%). Undiagnosed dementia was associated with increased 4-year mortality compared with no dementia in both countries. It was linked to younger age and absence of memory complaints, with marked socioeconomic and healthcare disparities in Brazil.

DISCUSSION: Undiagnosed dementia is common and associated with increased mortality, identifying a vulnerable population missed by current diagnostic pathways.