title: Obesity paradox in group 1 pulmonary hypertension: analysis of the NIH-Pulmonary Hypertension registry.
abstract: The 'obesity paradox' refers to the fact that obese patients have better outcomes than normal weight patients. This has been observed in multiple cardiovascular conditions, but evidence for obesity paradox in pulmonary hypertension (PH) remains sparse.
  
  
  
  We categorized 267 patients from the National Institute of Health-PH registry into five groups based on body mass index (BMI): underweight, normal weight, overweight, obese and morbidly obese. Mortality was compared in BMI groups using the χ2statistic. Five-year probability of death using the PH connection (PHC) risk equation was calculated, and the model was compared with BMI groups using Cox proportional hazards regression and Kaplan-Meier (KM) survival curves.
  
  
  
  Patients had a median age of 39 years (interquartile range 30-50 years), a median BMI of 23.4 kg m-2(21.0-26.8 kg m-2) and an overall mortality at 5 years of 50.2%. We found a U-shaped relationship between survival and 1-year mortality with the best 1-year survival in overweight patients. KM curves showed the best survival in the overweight, followed by obese and morbidly obese patients, and the worst survival in normal weight and underweight patients (log-rank P=0.0008). In a Cox proportional hazards analysis, increasing BMI was a highly significant predictor of improved survival even after adjustment for the PHC risk equation with a hazard ratio for death of 0.921 per kg m-2(95% confidence interval: 0.886-0.954) (P<0.0001).
  
  
  
  We observed that the best survival was in the overweight patients, making this more of an 'overweight paradox' than an 'obesity paradox'. This has implications for risk stratification and prognosis in group 1 PH patients.
authors.affiliation: Department of Medicine, University of Virginia, Charlottesville, VA, USA.
authors.forename: S
authors.initials: S
authors.lastname: Mazimba
authors.affiliation: Department of Medicine, University of Virginia, Charlottesville, VA, USA.
authors.forename: E
authors.initials: E
authors.lastname: Holland
authors.affiliation: Department of Medicine, University of Texas Medical Branch, Galveston, TX, USA.
authors.forename: V
authors.initials: V
authors.lastname: Nagarajan
authors.affiliation: Department of Medicine, University of Virginia, Charlottesville, VA, USA.
authors.forename: A D
authors.initials: AD
authors.lastname: Mihalek
authors.affiliation: Department of Medicine, University of Virginia, Charlottesville, VA, USA.
authors.forename: J L W
authors.initials: JLW
authors.lastname: Kennedy
authors.affiliation: Department of Medicine, University of Virginia, Charlottesville, VA, USA.
authors.forename: K C
authors.initials: KC
authors.lastname: Bilchick
mesh_terms: D000328:Adult; D015992:Body Mass Index; D005260:Female; D006801:Humans; D006976:Hypertension, Pulmonary / Q000150:complications* / Q000401:mortality* / Q000503:physiopathology; D056865:Ideal Body Weight / Q000502:physiology*; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D009316:National Institutes of Health (U.S.); D009765:Obesity / Q000145:classification / Q000150:complications / Q000401:mortality / Q000503:physiopathology; D050177:Overweight / Q000145:classification / Q000150:complications* / Q000401:mortality* / Q000503:physiopathology; D011379:Prognosis; D016016:Proportional Hazards Models; D012042:Registries; D018570:Risk Assessment; D014481:United States / Q000453:epidemiology