A Body Shape Index Outperforms Body Mass Index in Predicting All-Cause Mortality but Not Non-Fatal Cardiovascular Outcomes – Enah Study

Objective: Body mass index (BMI) is widely used to assess obesity-related risk but does not capture body fat distribution. A body shape index (ABSI), reflecting central adiposity, may better predict adverse outcomes. We compared the predictive value of BMI and ABSI for all-cause mortality and non-fatal outcomes. Design and method: This prospective cohort study, with a median follow-up period of 9.7 years (interquartile range 7.3–11.8), included 820 participants from the ENAH project. Participants were stratified into tertiles according to their ABSI z-scores. Cox regression models assessed associations of BMI z-score and ABSI z-score with all-cause mortality and a composite non-fatal cardiovascular, cerebrovascular, and renal outcome, adjusted for age, gender, smoking, hypertension, diabetes, and eGFR. Discrimination was evaluated using receiver operating characteristic (ROC) analysis. Non-fatal outcomes were cardiovascular (myocardial infarction, hearth failure, atrial fibrillation), cerebrovascular (CVI, TIA), renal (haemodialysis). Results: Across increasing ABSI tertiles, participants were older (47 vs 63 years), more often male (20% vs 42%), had higher waist circumference (88 vs 102 cm), lower eGFR (86.9 vs 79.3 mL/min/1.73 m2), and higher prevalence of hypertension (52% vs 74%) and diabetes (9.6% vs 16.5%) (all p<0.05), while BMI differed only modestly (28.1 vs 27.3 kg/m2, p=0.015). Outcome rates increased markedly across ABSI tertiles (31.0%, 35.4%, 50.9%; p<0.001). In adjusted Cox models, ABSI z-score was independently associated with all-cause mortality (HR 1.15 per SD, 95% CI 1.01–1.32; p=0.034), whereas BMI z-score was not (HR 0.95, 95% CI 0.79–1.14; p=0.595). In the combined model, ABSI remained significant (HR 1.15; p=0.041), while BMI did not (p=0.911). Neither ABSI nor BMI predicted non-fatal outcomes. Kaplan–Meier analysis showed a significant mortality gradient across ABSI tertiles (Log-rank p<0.001), but not across BMI tertiles (p=0.487). ROC analysis demonstrated superior distinction of all-cause mortality for ABSI compared with BMI (AUC 0.65 vs 0.51; difference in AUC 0.14; p<0.001), with no difference for non-fatal outcomes. Conclusions: ABSI strongly outperforms BMI in predicting all-cause mortality, while neither index predicts non-fatal cardiovascular, cerebrovascular, or renal outcomes. Central adiposity appears to be a more relevant determinant of long-term survival than overall body mass.