Higher Donor BMI Tied to Improved Lung Transplant Survival
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Lung transplant patients who received a lung from obese donors had a 15-20% reduction in mortality at 1 year in one of the first studies to examine the impact of donor body mass index (BMI) and post-transplant survival.

The BMI of lung transplant recipients has been shown to be an independent predictor of mortality, with studies showing an increased risk of death following transplant in patients who are either underweight or overweight, said researchers.

Close to 16,000 adult patients who received single- or double-lung transplants from 2005 to 2018 were included in the analysis. Median age of the lung recipients was 59, and roughly 60% were male. Donors were categorized as underweight (BMI less than 18.5), normal weight (18.5 to 25), overweight (25 to 30), class I obesity (30 to 35), class II obesity (35 to 40), and class III obesity (40.0).

Average donor BMI was 25.9, and 45% were classified as normal weight.

A survival benefit at 1 year was observed among patients who received a lung transplant from donors in obesity class 1 and obesity classes II/III compared with lungs from normal-weight donors, the researchers reported.

In adjusted analyses, the team reported lower odds of survival with increased donor age, male sex, and presence of diabetes.

These findings led the researchers back to the published literature in an effort to understand the possible mechanism involved. They found two studies -- one in rats and the other in deceased patients -- both of which suggested a role for obesity-related chronic adaption to hypoxic conditions.

In the rat study, lungs of young obese rats showed alveolar enlargement with diminished respiratory surface area when compared with those from normal-weight controls.

In the study of autopsy findings from 76 obese people matched to non-obese controls, alveolar capillary hemangiomatosis was exclusively seen in the obese subjects, with 72% exhibiting venous hypertension and capillary hemangiomatosis.

They said that although it is possible that the chronic hypoxic state associated with obesity may lead to advantages in lungs harvested from obese people, additional studies are still needed to confirm the association and further explore possible mechanisms.

Source: https://journal.chestnet.org/article/S0012-3692(20)34222-7/abstract