Not Enough Oxygen May Hurt Your Heart

Sleep apnea increases heart attack risk in long term study

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) Not getting enough oxygen during sleep can cause problems. This is the situation for many untreated sleep apnea patients. And one of those problems could affect the heart.

A recent study found an increased risk of heart attack among patients with obstructive sleep apnea.

Patients diagnosed with a moderate case of sleep apnea had an increased risk of dying from a heart attack.

Those with a lower oxygen saturation amount also had an increased risk of dying from a heart attack.

"Think you have sleep apnea? See a sleep doctor."

The study, led by Apoor S. Gami, MD, of Midwest Heart Specialists' Advocate Medical Group in Elmhurst, Illinois, looked at the heart-related risks of obstructive sleep apnea.

The researchers studied 10,701 adults who underwent a sleep study between 1987 and 2003.

These patients were followed for up to five years while researchers recorded any deaths that occurred from a heart attack.

The researchers also recorded the amount of oxygen the adults were breathing in at night, as well as their apnea-hypopnea index.

This index measures how many times patients stop breathing or slow their breathing considerably while asleep.

The score a person receives represents the number of times they stop breathing for at least 10 seconds or have a severe drop in blood oxygen for at least 10 seconds during one hour of sleep.

A score of 5 to 15 means the person has mild obstructive sleep apnea while a score of 15 to 30 is moderate and over 30 is severe.

During the average five years of follow-up, 142 patients died or had to be resuscitated from a heart attack.

The patients most likely to experience these heart attacks had a variety of risk factors.

These risk factors included being older, having high blood pressure, having coronary artery disease, having cardiomyopathy (weakening heart) or heart failure, certain types of an irregular heartbeat and reaching a low oxygen saturation of 10 percent in their sleep study.

The patients with the highest risk of having a fatal heart attack (or one requiring resuscitation) were 60 years old, had an apnea-hypopnea index of 20, had an average oxygen saturation level of 93 percent and had a low oxygen saturation of 78 percent.

A person whose oxygen saturation level drops to a low of 78 percent has an 80 percent increased risk of heart attack.

An apnea-hypopnea index of 20 is moderate obstructive sleep apnea, so even moderate cases can increase a person's risk of heart attack.

According to William Kohler, MD, the director of the Florida Sleep Institute in Spring Hill, Florida, and a dailyRx expert, sleep apnea can contribute to heart attacks in multiple ways.

"The sleep apnea causes heart attack not only because of the low oxygen but because additionally of the changes in body systems with the multiple awakenings that occur during sleep," Dr. Kohler said.

"There are complications in the autonomic nervous system that the multiple awakenings cause, basically causing additional stress on the physiologic system," he said.

"So it's not just the low oxygen alone that contributes to the heart attacks, but it's the general changes physiologically that occur from the multiple awakenings that occur with sleep apnea," Dr. Kohler said. "Sleep apnea can cause many significant medical problems and needs to be evaluated and treated appropriately."

The standard treatment for obstructive sleep apnea is continuous positive airway pressure, or CPAP, which is typically delivered to a person's airways through a face mask worn while the patient is asleep.

The machine requires a prescription and can cost anywhere from $150 to over $5,500. Most insurance plans will cover some or all of the expense of a CPAP machine and the mask, which ranges from $30 to $200.

The study was published June 11 in the Journal of the American College of Cardiology. The research was funded by the National Institutes of Health.

One author has consulted for RedMed, Medtronics and NeuPro and received grant funding from the Phillips-Respironics Foundation.

Another author has consulted for Medtronic, Boston Scientific and St. Jude Medical.

Reviewed by: 
Review Date: 
June 11, 2013
Last Updated:
August 7, 2013