Mortality among U.S. adults with coexisting type 2 diabetes mellitus and malignant neoplasms: A nationwide observational study (1999-2024).

Type 2 diabetes mellitus (T2DM) and malignant neoplasms are among the most prevalent chronic diseases worldwide. When coexisting, they substantially increase morbidity and mortality. However, national trends in mortality among patients with coexisting T2DM and malignant neoplasms in the United States remain underexplored. We analyzed U.S. death certificates from the CDC WONDER database for individuals aged ≥ 25 years who died between 1999 and 2024 with both T2DM and malignant neoplasms listed anywhere on the death certificate (underlying or contributing causes). Age-adjusted mortality rates (AAMRs) and annual percent change (APC) were calculated by year, sex, age group, race/ethnicity, geographic region, and urbanization status. From 1999 to 2024, 357,910 U.S. deaths occurred among individuals in whom both Type 2 Diabetes Mellitus and Malignant Neoplasms were listed on the death certificate. The AAMR rose from 6.37 to 17.2 per 100,000, with an overall APC of + 3.84%. Men exhibited higher mortality than women. Older adults bore the greatest burden, though middle-aged adults also showed a sharp proportional rise. Hispanic and Asian populations experienced the steepest increases. The West region showed the most pronounced growth. State-level variation exceeded fivefold, with Nebraska reporting the highest AAMR and Nevada the lowest. nonmetropolitan areas maintained higher mortality throughout, but metropolitan areas demonstrated a steeper rise, narrowing the rural-urban gap. Mortality among individuals with coexisting T2DM and malignant neoplasms has risen substantially in the U.S., with disproportionate increases among men, minority populations, and urban residents. These findings highlight the urgent need for integrated strategies addressing diabetes control, cancer prevention, and health equity across demographic and geographic subgroups.