Is there an obesity paradox in pulmonary arterial hypertension?

Background: Despite the deleterious health effects of obesity, an obesity paradox has been described in many diseases, including in heterogeneous populations with pulmonary hypertension. Whether obesity is associated with better outcomes in idiopathic (IPAH), drug and toxin-induced (DPAH) or heritable pulmonary arterial hypertension (HPAH) is not known. Methods: We assessed 1363 incident patients with IPAH, DPAH, and HPAH from the French Pulmonary Hypertension Registry. Cox proportional hazards regression was used to assess the effect of obesity on the risk of death or lung transplantation. Obesity was defined as body mass index (BMI)>30 kg/m2. Results: The prevalence of obesity was 30.7%. There was a higher proportion of females (66.6% vs 53.4%, p<0.01) and DPAH (30.5% vs 9.6%, p<0.01) among obese patients. Systemic hypertension, diabetes, and hypothyroidism were significantly more frequent among obese patients. Obese patients had a higher proportion in New York Heart Association class III (65.5% vs. 57.0%) but fewer were class IV (11.5% vs 16.7%)(p<0.01), and 6-minute walk distance was lower (278.3±119.6 vs. 322.3±145.3, p<0.01). Right atrial pressure, pulmonary wedge pressure and cardiac index were higher while pulmonary vascular resistance was lower in obese patients. Neither BMI (adjusted HR 0.99, 95%CI 0.97-1.01, p=0.41) nor obesity (adjusted HR 1.0, 95%CI 0.99-1.01, p=0.46) were predictive of death or transplantation in multivariate analyses. Conclusions: We found no association between obesity and survival in a large cohort of incident IPAH, DPAH and HPAH patients. Previous evidence of an obesity paradox in pulmonary hypertension may be related to other confounding factors.