Epidemiological studies have associated sleep apnea to heart disease in men, but the differences in risk between men and women have not been totally investigated. For this study, researchers measured sleep quality electronically in men and women with an average age of 63, who were free of any cardiovascular disease at the beginning of the study. They also tested all of them for troponin T, a protein that can be released into the bloodstream if there is damage to the heart, and whose presence in healthy people indicates an increased risk for heart disease.

They tracked the participants for a period of time, recording incidents of coronary artery disease, heart failure and death from cardiovascular disease or other causes. The study was published in Circulation. Obstructive sleep apnea was lone associated with increased troponin T, heart failure and death in women, but not in men. And in women, sleep apnea was associated with an enlarged heart, another risk factor for cardiovascular disease, but not in men.

"Most people who have sleep apnea have a lot of other risk factors for heart disease," said the lead author, Dr. Amil M. Shah, an assistant professor of medicine at Harvard. In women, the relationship between sleep apnea and heart disease continued even after summarizing for the other risks. Even among women with sleep apnea who don't get heart failure, it can be associated with changes in the heart that may lead to an even worst outcome." He added.