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28-10-2009 | Respiratory | Article

Obesity and underweight increase mortality risk after lung transplantation


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MedWire News: Obese and underweight patients have a higher mortality rate after undergoing lung transplantation than their normal-weight counterparts, US researchers have found.

Writing in the American Journal of Respiratory and Critical Care Medicine, David Lederer (Columbia University, New York) and team explain that, although previous studies have linked obesity to an increased risk for death after lung transplantation, these studies have not adequately controlled for potential confounding factors.

They also explain that little is known about the impact of being underweight on mortality after lung transplantation.

To address these issues, the researchers studied data on 5978 US adults with chronic obstructive pulmonary disease, cystic fibrosis, or diffuse parenchymal lung disease who underwent lung transplantation between 1995 and 2003.

Each participant’s body mass index (BMI) was recorded at the time of transplantation, with underweight defined as a BMI of less than 18.5 kg/m2, normal weight as a BMI of 18.5–24.9 kg/m2, overweight as a BMI of 25–29.9 kg/m2, and obese as a BMI of at least 30 kg/m2.

The researchers found that the overall mortality rate per 100 person-years was 15.6 in underweight, 14.0 in normal weight, 17.1 in overweight, and 18.4 in obese patients.

After adjustment for recipient and donor factors, such as demographics, diagnosis, diabetes mellitus, hypertension, smoking status, pre-operative steroid use, cause of death (donors only), and presence of bronchopulmonary infection, as well as transplant center, year of transplantation, allograft ischemic time, and other variables, the team found underweight, overweight, and obese patients were significantly more likely to die after lung transplantation than normal weight patients.

Indeed, underweight, overweight, and obese patients were, 15%, 15%, and 22%, respectively, more likely to die over a median post-transplant follow-up period of 4.2 years than patients with a normal weight.

Further analysis revealed that underweight and obesity together accounted for up to 12% of deaths in the first year after transplantation and 8% of deaths within 5 years.

Lederer and team conclude: “Both obesity and underweight are independent risk factors for death after lung transplantation.”

They add: “Prevention of underweight and obesity should be prioritized by primary care physicians and pulmonologists caring for patients with even early stages of these diseases.”

MedWire ( is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2009

By Mark Cowen

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