Moderate to severe obstructive sleep apnea increases the risk of coronary heart disease or death by 68% in men under the age of 70, but does not increase the risk for men over 70 or for women, researchers reported Monday. Previous studies have also found an increased risk of death linked to the night-time breathing disorder, but the studies have generally involved only small groups of patients, often those who are hospitalized, and most included few or no women. The new study, reported in Circulation: Journal of the American Heart Assn., is by far the largest study to date.