Long-term trends in DM and dementia-related mortality among middle-aged and elderly adults in the United States, 1999–2023: a nationwide population-based study

BACKGROUND: Diabetes mellitus (DM) and dementia frequently coexist in middle-aged and elderly people, jointly amplifying mortality risk. Clarifying long-term mortality patterns is essential for informing prevention and resource allocation. METHODS: We conducted a nationwide, population-based analysis using CDC WONDER Multiple Cause of Death data (1999-2023). Population mortality rates were calculated among decedents with both DM (ICD-10 E10-E14) and dementia (F01, F03, G30) recorded on the death certificate. Age-adjusted mortality rates (AAMRs) were standardized to the 2000 U.S. POPULATION: Temporal trends were evaluated using Joinpoint regression and ARIMA models stratified by sex, race/ethnicity, region, and urbanization. RESULTS: A total of 749,517 DM and dementia-related deaths occurred during 1999-2023, with AAMR rising from 12.05 to 30.95 per 100,000 (AAPC = 3.48%, P < 0.05). Males and NH Black individuals consistently demonstrated the highest mortality. Rural areas showed persistently elevated AAMRs, alongside marked interstate variation. CONCLUSION: DM and Dementia-related mortality among U.S. adults aged ≥ 45 years increased nearly 2.57-fold over the past two decades, with enduring sex, racial, and geographic disparities. Strengthening equitable, community-based preventive strategies and integrated metabolic-cognitive care is urgently needed.