132 The Open Obesity Journal, 2010, 2, 132-136 1876-8237/10 2010 Bentham Open Open Access Pulmonary Arterial Hypertension and Obesity † Wendell H. Williams III 1 , Robert E. Safford 2 , Michael G. Heckman 3 , Julia E. Crook 3 and Charles D. Burger *,1 1 From the Division of Pulmonary Medicine, Mayo Clinic, Jacksonville, Florida, USA 2 Division of Cardiovascular Diseases, Mayo Clinic, Jacksonville, Florida, USA 3 Biostatistics Unit, Mayo Clinic, Jacksonville, Florida, USA Abstract: Purpose: To examine the association between obesity and pulmonary arterial hypertension (PAH). Methods: This retrospective case-control study consisted of patients with PAH (N=207) and controls seen at a pulmonary clinic for reasons other than PAH (N=965). All patients were evaluated between 1992 and 2006 at Mayo Clinic in Jacksonville, Florida. Obesity was defined as body mass index (BMI) of 30 kg/m 2 or higher; class II obesity was defined as a BMI between 35.0 and 39.9 kg/m 2 , and class III obesity was defined as a BMI of 40.0 kg/m 2 or higher. Results: Obesity was present in 63 patients with PAH (30%) and 290 controls (30%). Class II or III obesity was present in 34 patients with PAH (16%) and 103 controls (11%), while class III obesity was present in 16 patients with PAH (8%) and 36 controls (4%). After adjustment for age, sex, and thyroid disease in logistic regression analysis, an association between obesity and PAH was not evident (odds ratio [OR], 0.97; P=.87), however non-statistically significant trends were observed toward an association between PAH and class II or III obesity (OR, 1.40; P=.14) and class III obesity (OR, 1.70; P=.11). Conclusions: Our findings do not indicate an association between PAH and obesity in WHO diagnostic group 1 patients. However trends were observed toward more severe class II and III obesity in PAH patients compared to controls, and this requires further study in larger samples. Keywords: Body mass index, obesity, prevalence, pulmonary arterial hypertension. INTRODUCTION In the United States, the prevalence of obesity has increased greatly during the past few decades [1]. In 2003- 2004, 33% of adults were obese [1]. Obesity has been linked to several serious systemic and cardiopulmonary diseases as well as to increased mortality [2-4]. The relationship bet- ween systemic hypertension and obesity is well established [5]. Whether individuals who are obese have a greater risk of developing pulmonary arterial hypertension (PAH) is unclear. It has been argued that obesity is not directly linked to PAH [6]. Indeed, Simonneau et al. [7] reported from the 2003 Third World Symposium on Pulmonary Arterial Hypertension, in agreement with the findings of the 1998 symposium on pulmonary hypertension (PH) [8], that obesity is an “unlikely” risk factor for PAH. In contrast, some obese patients, e.g., postmenopausal women, seem to be at increased risk of PAH [9]. In addition, obesity has been shown to correlate with elevated pulmonary artery systolic pressure (PASP) [10]. Most research on obesity and PH has focused on use of anorexic agents [11- *Address correspondence to this author at the Division of Pulmonary Medicine, Mayo Clinic, 4500 San Pablo Road, Jacksonville, FL 32224, USA; Tel: (904) 953-2381; Fax: (904) 953-2082; E-mail: burger.charles@mayo.edu † Portions of this manuscript have been published in abstract form by the American Journal of Respiratory and Critical Care Medicine, 2007. 13], sleep apnea [14, 15], and diastolic dysfunction [16]. The evidence suggests that these 3 conditions are all serious risk factors for PH. Obesity has been considered a possible confounding variable in all these studies. Overall, there is limited and conflicting literature on whether an association exists between PAH and obesity. The purpose of this study was to investigate the possible relationship between obesity and PAH in patients seen in the general pulmonary and PH clinics at Mayo Clinic. METHODS Data Collection This study was approved by the Mayo Clinic Institutional Review Board. Patient consent was not required by the Institutional Review Board for this “minimal risk” retrospective chart review. Consecutive patients with PAH seen in the PH Center from 1992 to 2006 at Mayo Clinic in Jacksonville, Florida, were studied retrospectively. The control group represented a random sample of patients seen over the same time period in the Pulmonary Clinic at Mayo Clinic for diseases other than PH; specifically, every tenth patient was selected for study inclusion. The following information was collected from patients in this retrospective study: age, sex, history of thyroid disease, weight, height, and body mass index (BMI). In patients without PAH, the principal complaint or condition prompting evaluation in the pulmonary clinic was recorded.