Do serum glucose and HbA1c levels predict mortality in patients with diabetes mellitus hospitalised for community-acquired pneumonia: Serum glucose and HbA1c levels and pneumonia-associated mortality in diabetes mellitus

Respiratory tract infections, which are among the most common infections, can be serious and fatal in patients with diabetes mellitus (DM). Studies show that community-acquired pneumonia (CAP) is more severe in people with DM. However, the impact of serum glucose and HbA1c levels on mortality associated with pneumonia remains controversial. We designed this study to investigate the impact of DM on the prognosis of pneumonia and to elucidate the relationship between glycaemic parameters and mortality in CAP. The study included a retrospective analysis of patients with CAP treated in the Chest Diseases Department and Intensive Care Unit (ICU) of Antalya Research and Training Hospital between January 2022 and June 2025. Patient demographics, clinical and laboratory parameters and clinical outcomes were analysed. The mortality rate of patients with DM was significantly higher than that of patients without DM (<i>p</i> = 0.028). When comparing discharged and deceased patients with DM, HbA1c and random blood glucose on admission were higher in the deceased patients (<i>p</i> = 0.012 and 0.019, respectively). Regression analysis identified C-reactive protein (<i>p</i> = 0.024), length of ICU stay (<i>p</i> = 0.005), HbA1c (<i>p</i> = 0.032), and Pneumonia Severity Index score (<i>p</i> = 0.008) as significant predictors of mortality. DM is not only a comorbidity but also a factor that strongly influences the clinical course of CAP. Our study confirms the finding that patients with DM have a poor prognosis and high mortality during the course of CAP. It also showed that HbA1c and blood glucose levels at admission are associated with mortality. As pneumonia may be more severe in patients with high blood glucose and HbA1c on admission, it should be considered that these patients with DM may need to be treated earlier in the ICU.