Heart transplant patients fare worse in areas with high levels of air pollution

Heart transplant patients who live in areas with high levels of air pollution had a 26% higher risk of mortality due to infection in a recent study of nearly 22,000 patients in the U.S.

The study, led by senior author Sanjay Rajagopalan, MD, a professor of medicine at Case Western Reserve University School of Medicine in Ohio, included data from 21,800 patients enrolled in the United Network for Organ Sharing/Organ Procurement and Transplantation Network. All patients were over the age of 18 when they underwent heart transplantation between 2004 and 2015, and 39% had heart failure due to prior ischemic disease.

“Given the fact that organ transplantation adds a tremendous cost to society, we had an interest in understanding if previously unknown environmental detriments adversely affected the outcomes of these patients,” Rajagopalan said in a release. “Long-term exposure to air pollution appears to pose amplified risks for heart transplant recipients.”

Rajagopalan et al. compared air levels of PM2.5—particulate matter commonly produced by power plants, cars and airplanes—between each patient’s ZIP code and the U.S. National Ambient Air Quality Standards (NAAQS). Around 21.9% of the study population were living in areas where PM2.5 levels exceeded NAAQS limits for clean air.

The authors reported in the Journal of the American College of Cardiology that ZIP codes with higher concentrations of air pollution also had larger populations, more minorities, higher unemployment rates and more households. Transplant recipients who had long-term exposure to air pollution over several years saw a 26% increased risk of mortality from infection for each 10 microgram-per-cubic-meter increase in PM2.5 levels.

After nearly five years of follow-up, 23.9% of patients in the study died. Rajagopalan and colleagues said their established link between air pollution and mortality remained consistent across subgroups.

“This study makes an important contribution to our understanding of the health effects of air pollution,” C. Arden Pope III, PhD, wrote in an accompanying editorial. “It used a straightforward approach to evaluate health effects of air pollution in a unique cohort of individuals in a vulnerable health state. It provides intriguing evidence that exposure to air pollution substantially contributes to mortality risk in cardiac transplant patients.”