Diabetes and psoriasis are known to increase the risk of each other, yet their combined impact on long-term mortality remains unclear. This prospective cohort study examined the associations between the coexistence of diabetes and psoriasis and all-cause and cause-specific mortality in a nationally representative sample of U.S. adults. Data were obtained from 16,852 participants in the National Health and Nutrition Examination Surveys (NHANES). Survival was assessed using the Kaplan-Meier method, and a weighted Cox proportional hazards model was employed. In fully adjusted models (adjusted for age, sex, race, BMI, smoking status, and comorbidities), individuals with both diabetes and psoriasis demonstrated significantly increased risks of all-cause mortality (hazard ratio [HR]: 1.76, 95% confidence interval [CI]: 1.04-3.00) and cancer-specific mortality (HR: 2.90, 95% CI: 1.28-6.54), but not cardiovascular mortality (HR: 0.87, 95% CI: 0.18-4.35). Comorbidity was significantly associated with elevated risks of all-cause and cancer mortality (P < 0.05). These findings suggest a notable association between the coexistence of these two chronic conditions and elevated overall and cancer mortality risks, while no significant effect was found on cardiovascular mortality. Exploratory analyses also indicated a possible dose-response relationship between psoriasis severity and cardiovascular mortality, warranting further investigation.
