Survival advantages of excess body mass index in patients with idiopathic pulmonary arterial hypertension

OBJECTIVE: An obesity paradox, a "paradoxical" decrease in morbidity and mortality with increasing body mass index (BMI), has been shown in patients with heart failure. However, the impact of BMI in patients with idiopathic pulmonary arterial hypertension (IPAH) has not been studied. This study aims to find out whether BMI is a prognostic factor in IPAH. METHODS AND RESULTS: We analysed 173 patients with IPAH. The patients were subclassified into categories of BMI defined as: under-weight (< 18.5 kg/m2), normal weight (18.5 to 24.9 kg/m2), overweight and obese (25 to 34.9 kg/m2). The three BMI groups had similar profiles in terms of haemodynamic parameters assessed by right heart catheterization and level of NT-proBNP. The overweight and obese group had higher age, and lower WHO functional class, larger left ventricular end-diastolic dimensions (LVEDDs) than the other two groups.The Kaplan-Meier survival curves for the three BMI categories demonstrated that the overweight and obese group had a significantly higher survival rate than the normal weight and underweight groups (log-rank test, P = 0.027, P = 0.000, respectively). In a stepwise forward regression, lower BMI, higher WHO functional class, lower cardiac index, smaller LVEDDs and absence of targeted medication remained independent predictors of mortality. CONCLUSIONS: Excess body mass is a protective factor for death in patients with IPAH.