Hemoglobin glycation index and mortality risk in severe community-acquired pneumonia: a retrospective study

Background: The hemoglobin glycation index (HGI), which reflects discrepancies between glycosylated hemoglobin (HbA1c) and fasting plasma glucose (FPG), has been linked to poor outcomes across various diseases. This study aims to clarify its prognostic value in patients with community-acquired pneumonia (CAP), a critical concern for clinicians, by evaluating the association between HGI and all-cause mortality in CAP requiring intensive care unit (ICU) monitoring, specifically examining potential non-linear relationships and subgroup-specific effects. Methods: The Medical Information Mart for Intensive Care IV (MIMIC-IV) database was used for this retrospective cohort analysis. HGI was calculated by linear regression of HbA1c on FPG. Kaplan-Meier and Cox regression analyses were used to evaluate the association between HGI and all-cause mortality. Restricted cubic spline (RCS) and threshold effect analyses examined non-linear relationships, and subgroup analyses explored effect heterogeneity. Results: The research enrolled a cohort of 1,674 individuals diagnosed with CAP for investigation. The all-cause mortality rates of patients within 30 days and 90 days were 25.08% and 33.92% respectively. We divided the patients into four groups (Q1-Q4) based on quartiles. Cox regression showed that Q3 had the lowest mortality risk at 30 days [hazard ratio (HR) =0.46; 95% confidence interval (CI): 0.29-0.74; P