Shifting competing underlying causes of death among U.S. decedents with diabetes recorded as a non-underlying cause, 1999–2024

Objective To examine U.S. trends and underlying-cause patterns among deaths with diabetes recorded as a non-underlying cause (DM-nonUCD). Methods We used CDC WONDER Multiple Cause of Death data from 1999 to 2024. DM-nonUCD was defined as deaths with ICD-10 codes E10-E14 in multiple-cause fields, excluding deaths with diabetes as the underlying cause. Analyses were performed overall and for type 1 diabetes (E10) and type 2 diabetes (E11). Death counts, age-adjusted mortality rates (AAMRs), and Joinpoint trends were assessed. Results DM-nonUCD occurred in 4,794,136 deaths and increased from 141,371 in 1999 to 246,426 in 2024. The leading underlying causes were circulatory diseases (2,294,799; 47.87%), malignant neoplasms (725,592; 15.13%), and respiratory diseases (449,837; 9.38%). Circulatory diseases remained dominant but declined from 60.51% to 44.48%, with decreasing AAMR (average annual percent change [AAPC], -1.01%; 95% CI, -1.21 to -0.88). Shares increased for malignant neoplasms (14.01% to 16.30%), nervous system diseases (2.67% to 7.56%), and mental and behavioral disorders (1.05% to 4.41%). Within circulatory causes, ischemic heart disease AAMR declined (AAPC, -2.04%; 95% CI, -2.23 to -1.92), whereas hypertensive disease AAMR increased (AAPC, 3.21%; 95% CI, 2.94 to 3.56). Subtype analyses showed similar cause-distribution shifts for E10- and E11-nonUCD, with declining circulatory shares and increasing nervous system and mental and behavioral shares. Conclusions DM-nonUCD represents a substantial proportion of deaths in which diabetes was recorded on the death certificate. The underlying-cause profile is shifting from coronary-dominated mortality toward broader multimorbidity, supporting surveillance and health-system planning that consider competing causes beyond ischemic heart disease.