Anthropometric parameters and long-term mortality in patients admitted for acute myocardial infarction: results from FAST-MI registries

Introduction The relationship between anthropometric parameters and long-term mortality following acute myocardial infarction (AMI) remains debated. This is particularly true regarding the "obesity paradox," where a higher body mass index (BMI) appears to be associated with better outcomes. Whether assessing abdominal adiposity can resolve this paradox by better reclassifying long-term risk remains unclear. Purpose To investigate the association of multiple anthropometric measurements with long-term post-AMI mortality using the FAST-MI program. Methods The FAST-MI program consists of three nationwide French surveys conducted 5 years apart (2005, 2010 and 2015), including consecutive patients admitted for AMI with up to 8-year follow-up. We used two categories of anthropometric measurements: traditional metrics (height, weight, and BMI) and abdominal adiposity markers (waist circumference [WC], WC/BMI ratio, WC/height ratio, and body roundness index [BRI]). We assessed their relationship with 8-year mortality by using multivariable Cox models. Results A total of 12,241patients were included for weight, height and BMI analyses, and 5,968 for analyses using WC. After adjustment, neither weight (aHR 0.999 per kg, 95%CI 0.997-1.002, p=0.46) nor BMI (aHR 1.004 per kg/m2, 95%CI 0.996-1.011, p=0.32) were associated with 8-year mortality; while height showed an inverse association with 8-year mortality (aHR 0.992 per cm, 95%CI 0.887-0.997, p=0.003). All abdominal adiposity markers were associated with increased 8-year mortality after AMI; WC (aHR 1.007 per unit, 95%CI 1.004-1.020), BRI (aHR 1.058 per unit, 1.036-1.081), and WC/BMI (aHR 1.32 per unit, 95%CI 1.19-1.47) (all p<0.001). In a sensitivity analysis excluding patients with BMI <18.5 kg/m2, BMI was associated with 8-year mortality (aHR 1.013 per kg/m2, 95%CI 1.005-1.020, p=0.001), confirming a U-curve effect, whereas findings for abdominal metrics remained unchanged. When BMI and WC/BMI were analyzed together, both the U-shaped extremes of BMI (<18.5 and >35 kg/m²) and the highest WC/BMI quintile (derived specifically within each sex and BMI category) emerged as independent predictors of 8-year mortality (Figure). Conclusion After AMI, the apparent "obesity paradox" is explained by a U-shaped relationship between BMI and mortality, rather than a true protective effect of excess weight. Abdominal adiposity metrics like WC/BMI independently outperform standard BMI in predicting long-term survival. These results highlight the critical need to incorporate central obesity measurements into routine post-MI patient management.