"This study shows that COPD, even in its mildest form, is associated with diminished heart function," Susan B. Shurin, MD, acting director of the National Heart, Lung, and Blood Institute of the National Institutes of Health, which funded the research, says in a news release. "We now have evidence that the presence of even mild COPD may have important health implications beyond the lungs."
Researchers say heart failure caused by lung disease is well documented in people with severe COPD, but this is the first study to show a link between mild forms of lung disease and impaired heart function.
"We found that there appears to be a linear relationship between lung function and heart function, and even a small hit to the lungs negatively affects heart function as well," says researcher Graham Barr, MD, DrPH, assistant professor of medicine and epidemiology at Columbia University Medical Center, in the news release.
"These results raise the intriguing possibility that treating lung disease may, in the future, improve heart function," says Barr. "Further research is needed to prove whether treating mild COPD will help the heart work better."
COPD is the fourth leading cause of death in the U.S. and is strongly related to smoking. It includes the conditions of emphysema and chronic bronchitis. COPD makes it progressively more difficult to breathe.
The study, published in the New England Journal of Medicine, used magnetic resonance imaging (MRI) to measure heart function in 2,816 adults aged 45 to 84. Of the participants, 13% were smokers, 38% were former smokers, and 49% never smoked.
The extent of emphysema in the participants was also determined with breathing tests and images of the chest.
The results showed the link between lung disease and impaired heart function was strongest in current smokers. But researchers also found an association between mild emphysema and decreased heart function in people who had never smoked.
"We used sensitive measures to pick up small differences in healthy people," says Barr. "We demonstrated that even mild COPD is associated with subclinical reductions in heart function, probably since not enough blood is entering the heart due to vascular problems in the lungs."