Obesity Attenuates the Association Between the Modified Five-Item Frailty Score and Mortality in Septic Surgical...

Obesity is an independent predictor of mortality in septic surgical patients, likely associated with underlying physiologic frailty, measured by the modified 5-item frailty index (mFI-5). This study aimed to determine the prevalence of frailty among obese and nonobese surgical patients and evaluate the impact of frailty on mortality in these populations.

We performed a single-center retrospective cohort study of surgical intensive care unit patients admitted with sepsis (sequential organ failure assessment, SOFA ≥2). Individual mFI-5 scores (range 0-5) were calculated and the prevalence of prefrailty (mFI <2), moderate-frailty (mFI = 2), and severe-frailty (mFI ≥3) across body mass index (BMI) categories (underweight, nonobese, class I-III obesity) was compared. BMI <18.5 kg/m² was excluded. Characteristics associated with mFI ≥2 were evaluated. Factors independently associated with frailty, incorporating demographic, socioeconomic, and clinical variables were identified. Four cohorts were made: obese (BMI ≥30 kg/m², n = 766) and nonobese (18.5-29.9 kg/m², n = 574), further divided into frail (mFI≥2) and prefrail (mFI <2). In-hospital mortality, cumulative 90-day mortality, and 90-day survival were compared across groups.

Severe frailty was highly associated with increasing BMI class, occurring in 37% of morbidly obese patients versus 19% of nonobese patients (P < 0.005). Increasing BMI independently predicted moderate-to-severe frailty (odds ratio [OR]: 1.04, 95% confidence interval [CI]: 1.02-1.05). Frailty significantly increased 90-day mortality in nonobese patients (17.4% versus 36.4%, P < 0.005) but not in obese patients (34% versus 35%). Nonfrail nonobese patients demonstrated superior 90-day-survival.

Obesity is highly associated with higher mFI-5 scores, though its prognostic impact appears attenuated in obese versus nonobese cohorts, suggesting the need for more discriminatory frailty tools in the obese population.