According to research presented at the American College of Cardiology annual conference in Washington, D.C., clinicians might want to wait to administer sleep apnea tests to patients who have recently suffered heart attacks.

A total of 52 percent of patients tested positive for sleep apnea in the initial test. Forty-two percent had , the most common form of the disorder, in which the airway is blocked for brief periods by the tongue or throat muscles. Ten percent had central sleep apnea, a less common form in which the brain fails to properly signal the muscles that control breathing.

About a quarter of the patients underwent a second sleep study after six months. A majority of the patients initially found to have sleep apnea showed a change of status in the follow-up sleep study. Among those initially diagnosed with obstructive sleep apnea, 46 percent no longer had sleep apnea at the 6-month test. Among those initially diagnosed with central sleep apnea, 83 percent were found to have obstructive sleep apnea at the 6-month test. The vast majority (93 percent) of those initially found to have no sleep apnea remained apnea-free at six months.