Obesity and septic patient outcomes: Shaping the puzzle through age and sex perspectives

Abstract

While obesity has been reported as a protective factor in septic patients, little is known about the potential modifying effects of age and sex. The objective of this study is to investigate age and sex-specific associations between obesity and the prognosis of septic patients. A retrospective analysis was conducted on a cohort of 15,464 septic patients, categorized by body mass index (BMI) into four groups: underweight (<18.5kg/m2, n=483), normal (18.5-24.9kg/m2, n=4344), overweight (25-29.9kg/m2, n=4949) and obese (≥30kg/m2, n=5688). Multivariable logistic regression and inverse probability weighting were employed to robustly confirm the protective effect of a higher BMI on 28-day mortality, with normal weight serving as the reference category. Subgroup analyses based on age (young: 18-39, middle-aged: 40-64 and elderly: ≥65) and sex were performed. The findings demonstrate that high BMI independently confers a protective effect against 28-day mortality in septic patients. However, the relationship between BMI and 28-day mortality exhibits a non-linear trend, with a BMI of 34.5kg/m2 displaying the lowest odds ratio. Notably, the survival benefits associated with a high BMI were not observed in the young group. Moreover, being underweight emerges as an independent risk factor for middle-aged and elderly female patients, while in males it is only a risk factor in the elderly group. Interestingly, being overweight and obese were identified as independent protective factors in middle-aged and elderly male patients, but not in females. The effect of BMI on mortality in septic patients varies according to age and sex. Elderly individuals with sepsis may derive more prognostic benefits from obesity.