Original Article

International Journal of Obesity advance online publication 21 March 2017; doi: 10.1038/ijo.2017.45

Obesity paradox in group 1 pulmonary hypertension: analysis of the NIH-Pulmonary Hypertension registry

S Mazimba1, E Holland1, V Nagarajan2, A D Mihalek1, J L W Kennedy1 and K C Bilchick1

  1. 1Department of Medicine, University of Virginia, Charlottesville, VA, USA
  2. 2Department of Medicine, University of Texas Medical Branch, Galveston, TX, USA

Correspondence: Dr S Mazimba, Department of Medicine, Division of Cardiovascular Medicine, University of Virginia, PO Box 800158, Charlottesville, VA 22908-0158, USA. E-mail: SM8SD@hscmail.mcc.virginia.edu

Received 9 December 2016; Revised 2 February 2017; Accepted 9 February 2017
Accepted article preview online 17 February 2017; Advance online publication 21 March 2017

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Abstract

Background:

 

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.

Methods:

 

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 χ2 statistic. 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.

Results:

 

Patients had a median age of 39 years (interquartile range 30–50 years), a median BMI of 23.4kgm2 (21.0–26.8kgm−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 kgm−2 (95% confidence interval: 0.886–0.954) (P<0.0001).

Conclusion:

 

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.

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