Clinical Outcomes of Urinary Tract Infection and Pneumonia in Hospitalized Patients with Type 1 and Type 2 Diabetes

Abstract

Background: Individuals with diabetes have an increased risk of infection-related hospitalization; however, whether type 1 diabetes (T1D) and type 2 diabetes (T2D) differentially influence outcomes following hospitalization remains unclear. We compared mortality, metabolic complications, and hospital outcomes among adults with T1D, T2D, or no documented diabetes admitted with urinary tract infection (UTI) or pneumonia. Methods: We performed a retrospective cohort study using electronic health records from a tertiary 1500-bed medical center (2018–2026). Eligible adult hospital admissions for UTI or pneumonia were classified according to documented T1D, T2D, or no diabetes. The study included 22,475 UTI admissions (211 with T1D, 9230 with T2D, and 13,034 without diabetes) and 32,703 pneumonia admissions (208 with T1D, 15,112 with T2D, and 17,383 without diabetes). Multivariable logistic regression was used to evaluate the association between diabetes status and 30-day mortality, with adjustment for age, sex, BMI, CCI, and MEWS. Because individuals could contribute multiple eligible admissions, the primary mortality models used patient-level cluster-robust standard errors to account for within-patient correlation. Results: T1D admissions involved substantially younger individuals than T2D or non-diabetes admissions but were associated with the greatest metabolic instability during hospitalization. Hypoglycemia occurred in 41.2% of T1D admissions for UTI and 19.7% for pneumonia, compared with 19.6% and 4.1% in T2D, respectively (both p < 0.001). Hyperglycemia was also markedly more frequent in T1D, affecting 88.6% of UTI and 72.6% of pneumonia admissions. ICU transfer was nearly threefold higher in T1D than T2D during UTI hospitalization (10.0% vs. 3.5%, p < 0.001). After adjustment, T1D was not independently associated with 30-day mortality, whereas T2D was associated with modestly lower adjusted odds of 30-day mortality compared with patients without documented diabetes. No significant mortality differences were observed between T1D and T2D. Conclusions: Diabetes type was not independently associated with higher short-term mortality following hospitalization for UTI or pneumonia after adjustment for measured confounders. However, T1D was associated with substantially greater glycemic instability and increased intensive care utilization, suggesting that diabetes type may influence the metabolic complexity and intensity of inpatient management more than short-term survival.