About one in five U.S. adults over the age of 45 has a lung condition that—even in its mildest forms—can have a negative impact on the heart, researchers announced today.

This common disease, chronic obstructive pulmonary disease (COPD), is also the fourth leading cause of death in the U.S. and includes ailments in which lung tissue dies or airways are narrowed, such as emphysema or chronic obstructive bronchitis. It is often associated with smoking, and in severe cases it has been linked to heart problems.

"Heart failure caused by lung disease is well documented in patients with severe COPD but was not thought to occur in patients with mild COPD," Graham Barr, an assistant professor of medicine and epidemiology at Columbia University Medical Center in New York City, said in a prepared statement.

He and his colleagues set out to see whether low-level COPD might also have an effect on heart performance. As part of a larger heart study, the Multi-Ethnic Study of Atherosclerosis (MESA), the researchers assessed the lung and heart capacities (via computed tomography scans and magnetic resonance imaging) of 2,816 relatively healthy 45- to 84-year-old adults who didn't have cardiac disease or severe COPD.

"There appears to be a linear relationship between lung function and heart function," said Barr, who was the lead author on the study, published online January 20 in the New England Journal of Medicine. "Even a small hit to the lungs negatively affects heart function." The deterioration of heart efficiency was likely because "not enough blood is entering the heart due to vascular problems in the lungs," he added. The relationship between the lung disease and, as the study authors describe it, "significant decrements in left ventricular filling and cardiac output," held true in this population-based study across current smokers (13 percent of subjects), former smokers (38 percent) and those who had never smoked (49 percent).

Although the discovery might mean that mild and moderate heart dysfunction is even more common than previously estimated, it might also lead to new treatments—and the knowledge that improvements in one system might help the other. "Our next step is to directly measure vasculature damage in the lungs and then determine whether cardiac therapies may help lung disease and vice versa," Barr said.

In the meantime, the results might generate more research into all levels of COPD—not just the most sever cases. "We now have evidence that the presence of even mild COPD may have important health implications beyond the lungs," Susan Shurin, acting director of the National Heart, Lung and Blood Institute at the National Institutes of Health (which funded the research), said in a prepared statement.

The findings may also help raise the profile of the disease, which could be important for the millions of people who have moderate or mild COPD but are not aware of it—by some estimates this is about half of all people with the disease. "COPD is one of the big killers in the United States, yet it is unknown to many," James Kiely, director of the National Heart, Lung and Blood Institute's Division of Lung Diseases, said in a prepared statement. "Unfortunately, many people with COPD don't recognize common symptoms," which include shortness of breath, fatigue and wheezing. 

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