Impact of Diabetes Mellitus on Disease Severity and Mortality in Acute Pancreatitis: A Retrospective Single-Center Cohort Study

<b>Background:</b> Diabetes mellitus (DM) is a condition that may increase the severity of acute pancreatitis (AP) through chronic inflammation and disturbances in immune responses. However, the independent effect of DM on clinical outcomes in AP has not yet been fully elucidated. <b>Methods:</b> In this retrospective cohort study, 492 patients diagnosed with acute pancreatitis at the Gastroenterology Clinic of Ankara Bilkent City Hospital between January 2022 and March 2025 were included. Patients were divided into two groups based on the presence of diabetes, and outcomes were compared using statistical methods. <b>Results:</b> Of the total 492 patients (mean age 58.6 ± 17.2 years; 50.2% female) included, 98 (19.9%) had DM. Moderate-to-severe AP occurred in 67.3% of diabetic versus 37.8% of non-diabetic patients (<i>p</i> < 0.0001), and severe disease developed more frequently in the diabetic group (6.1% vs. 1.0%, <i>p</i> = 0.0057). Systemic complications were significantly more common in patients with diabetes (45.9% vs. 26.9%, <i>p</i> = 0.0004). Hospital mortality was higher among patients with diabetes (9.2% vs. 4.6%, <i>p</i> = 0.0344), and Kaplan-Meier analysis demonstrated numerically lower overall survival in patients with diabetes (log-rank <i>p</i> = 0.095), with early divergence in survival curves. Cox proportional hazards analysis confirmed diabetes as an independent predictor of in-hospital mortality (adjusted HR 2.64, 95% CI 1.17-5.97; <i>p</i> = 0.019). After adjustment for confounders, diabetes remained independently associated with the development of moderate/severe pancreatitis (adjusted OR 2.00, 95% CI 1.24-3.22; <i>p</i> = 0.004). Diabetes also independently predicted in-hospital mortality (adjusted OR 3.36, 95% CI 1.35-8.34; <i>p</i> = 0.009), along with APACHE II score. ROC analysis demonstrated that adding diabetes mellitus to the APACHE II score significantly improved mortality prediction compared with APACHE II alone (AUC 0.785 vs. 0.724). The retrospective and single-center design of this study may limit its generalizability and create potential selection bias. There were insufficient data on the type of diabetes, its duration, and glycemic control (e.g., HbA1c), and therefore, we could not assess these factors, all of which may influence risk estimates. Although the survival curves showed early divergence, the borderline log-rank significance (<i>p</i> = 0.095) highlights the limited statistical power to detect long-term survival differences in this cohort. <b>Conclusions:</b> DM is associated with substantially increased severity and in-hospital mortality in AP, primarily through an elevated risk of systemic organ failure. Incorporation of diabetes status into early severity stratification may improve prognostic accuracy and guide closer monitoring and timely interventions in this high-risk population.