People with sleep apnea are more likely to die of a heart attack during the night, compared to the rest of the population. The peak time is in the early morning up to noon. This is because of daily fluctuations in the physiology of the heart and circulation. However this is not so in the case of sleep apnea, according to a study from the Mayo Clinic Sleep Center.
Because people that suffer with sleep apnea stop breathing multiple times in the night because of obstruction to their upper airway, it is linked to heart problems.
In a study, funded by the National Heart, Lung and Blood Institute (NHLBI), 10,701 people who participated in sleep studies were followed for an average of 5.3 years for incidence of sudden cardiac death. In that time, 142 patients died of sudden cardiac death. The most common predictors were an age of 60 or older, 20 or more apnea episodes per hour of sleep, and an oxygen saturation below 78 percent during sleep.
"What we found that is new with this study is that if you have sleep apnea, your risk of sudden death increases almost twofold, particularly if you stopped breathing more than 20 times per hour of sleep and if you had severe falls in oxygen saturation during sleep," says senior author Virend Somers, M.D., Ph.D., a Mayo Clinic cardiologist.
When a person is breathing properly, the oxygen saturation level — when air flows through the lungs — during sleep is 100 percent, Dr. Somers says. This study showed that if a person is not breathing properly and the oxygen saturation level falls to as low as 78 percent, the risk of sudden cardiac death significantly increases, he says.
Lead author Apoor Gami, M.D., says Mayo Clinic's previous research showed that people with sleep apnea have a much higher risk of sudden cardiac death between midnight and 6 a.m., when people are typically asleep, while people without sleep apnea die more often from sudden cardiac death between 6 a.m. and noon.