Impact of Diabetes Mellitus on 30-Day Mortality and Ventilation Outcomes in Critically Ill Patients with Acute Exacerbation of Chronic Obstructive Pulmonary Disease (AECOPD): A Retrospective Cohort Study

<b>Background:</b> Acute exacerbations of chronic obstructive pulmonary disease (AECOPD) are a major cause of intensive care unit (ICU) admissions and are associated with substantial short-term mortality. Diabetes mellitus is a frequent comorbidity in patients with COPD, yet its impact on short-term outcomes in critically ill AECOPD patients remains uncertain. <b>Aim:</b> The aim of this study was to investigate whether diabetes mellitus is independently associated with 30-day mortality in critically ill adult patients admitted to the ICU with AECOPD. <b>Methods:</b> We conducted a retrospective cohort study of adult ICU patients with AECOPD using the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. All eligible adult patients with a documented diagnosis of AECOPD during the study period were included. Patients were categorized according to the presence or absence of diabetes mellitus. Diabetes mellitus was identified based on documented diagnostic codes and clinical records at the time of ICU admission. Demographic variables, laboratory parameters obtained within the first 24 h of ICU admission, and mechanical ventilation requirements were assessed. Mechanical ventilation was initiated according to standard clinical indications, including acute respiratory failure, hypoxemia, or hypercapnia. The primary outcome was 30-day all-cause mortality. Kaplan-Meier survival analysis, multivariable logistic regression, and Cox proportional hazards models were applied to identify independent predictors of mortality. <b>Results:</b> A total of 5874 ICU patients were included, of whom 2489 (42.3%) had diabetes. Patients with diabetes were slightly younger, more frequently male, and more often received mechanical ventilation than non-diabetic patients. Unadjusted 30-day mortality was lower among diabetic patients (15.3% vs. 17.5%; <i>p</i> = 0.032). However, after adjustment for relevant covariates, diabetes was not an independent predictor of 30-day mortality (HR = 0.80; <i>p</i> = 0.46). Age, male sex, and elevated lactate levels were associated with increased mortality, while early mechanical ventilation showed an association with improved short-term survival. <b>Conclusions:</b> Diabetes mellitus was not independently associated with 30-day mortality in critically ill patients with AECOPD. Short-term outcomes were primarily influenced by age, markers of metabolic stress, and timely ventilatory support. Due to limitations of the database, reliable differentiation between type 1 and type 2 diabetes mellitus and detailed assessment of COPD severity or phenotype were not consistently feasible. Further prospective studies are warranted to clarify the long-term implications of diabetes in this patient population.