Association between base excess and mortality in septic older adults

Aim Septic older adults represent a vulnerable population with high mortality rates. Base excess (BE), an indicator of acid–base status, may serve as a prognostic marker in sepsis. This study aimed to investigate the association between BE and mortality in septic older adults. Methods A retrospective analysis included septic older adults (age ≥ 65 years) from the Medical Information Mart for Intensive Care (MIMIC)‐IV database. The primary outcome was 30‐day mortality. Multivariate Cox regression models and Kaplan–Meier analysis were used to assess the association between BE and 30‐day mortality. A two‐segment linear regression model with smooth curve fitting was employed to examine threshold effects of BE on clinical outcomes. Results The study comprised 7379 participants, with a 21.8% 30‐day mortality rate and an 18.6% in‐hospital mortality rate. A nonlinear, U‐shaped relationship ( P < 0.001) was observed between BE and 30‐day mortality in septic older adults, indicating increased risk with higher or lower BE levels. Various BE groups showed different hazard ratios for mortality: 2.7 (2.26–3.22), 1.86 (1.65–2.09), 1.41 (1.19–1.67), and 1.9 (1.4–2.58), respectively, compared with the reference group (−3 mEq/L ≤ BE < 3 mEq/L). The inflection point was calculated as 0.5 mEq/L. Conclusions Our findings suggest a U‐shaped relationship between BE and mortality in septic older adults, emphasizing the importance of monitoring acid–base status in sepsis management for this population. Geriatr Gerontol Int 2025; ••: ••–•• .