Individuals on long-term oxygen therapy (LTOT) for chronic obstructive pulmonary disease have been found to face greater risk of death from other cardiovascular and respiratory diseases, according to a new study published in the American Journal of Respiratory and Critical Care Medicine.

Researchers enrolled 7,600 patients who had started long-term oxygen therapy for COPD from 1987 to 2004 and studied them until LTOT was suspended or until death—for a median length of 1.7 years. They ultimately found that while the risk of death decreased annually for both respiratory disease (2.7%) and lung cancer (3.4%), there were annual increased risks of circulatory disease (2.8%) and digestive organ disease (7.8%).

“The mechanism that underlies the increases in both overall mortality and mortality due to non-respiratory causes is that the patients have a progressively higher burden of coexisting diseases and conditions, and become more vulnerable with increasing age,” said researcher Dr. Magnus P. Ekström. “Physicians who treat COPD with LTOT need to be aware of these shifts and to monitor for other conditions that may influence the risk of death in these patients.”