In obstructive sleep apnea, the upper airway becomes completely or partially blocked, interrupting regular breathing, several times per night.
The new study, published in the Journal of the American College of Cardiology, recommends that people who have heart attacks while sleeping at night be screened for obstructive sleep apnea.
The study included 92 people who had recently had a heart attack.
The patients reported what time their heart attack symptoms started. They also took part in a sleep study about 17 days after their heart attack. The sleep study showed that 64 patients had obstructive sleep apnea.
The patients with obstructive sleep apnea were six times more likely to have had their heart attack between midnight and 6 a.m. than during the rest of the day. In contrast, the patients without sleep apnea were more likely to have had their heart attack between 6 a.m. and noon.
Obstructive sleep apnea "may be a trigger" for heart attacks, write the researchers, who included the Mayo Clinic's Fatima Kuniyoshi, PhD. Kuniyoshi's team calls for further studies to see if obstructive sleep apnea treatment reduces heart attack risk, especially at night.