Sleep Apnea May Trigger Nighttime Heart Attacks

By Paula Rasich
Reviewed by Elizabeth Klodas, MD, FACC

(CardioSmart) People with the sleep disorder obstructive sleep apnea (OSA) are more likely to have a heart attack between 12 and 6 a.m. than during any other time of the day, a new study finds.

OSA is a common condition in which a person stops breathing for short periods during sleep, most often because the tongue and other tissue in the back of the throat collapse and block the airway. The absence of airflow causes a loss of oxygen in the blood, which can lead to a disturbed heart rhythm as well as higher blood pressures as the person struggles to breathe. OSA is associated with an increased risk of hypertension, heart attack, stroke, and heart failure.

In the study, a team of researchers at the Mayo Clinic in Rochester followed 92 heart attack patients, 64 of whom were subsequently diagnosed with OSA. Three quarters of the patients were men, and all were overweight or obese. They found that heart attacks occurred between 12 am and 6 am in 32% of patients with OSA, compared with only 7% of patients without OSA. In addition, the odds of having OSA in those patients whose heart attack occurred in the nighttime hours were six-fold higher than for any other 6-hour period of the day. Additionally, of all patients who suffered a heart attack between 12 and 6 a.m., 91% had OSA.

“These findings suggest that obstructive sleep apnea may be a trigger for heart attack,” says study author Virend Somers, MD, PhD. “People with nocturnal onset of heart attack should be evaluated for sleep apnea, and future research should address the effects of obstructive sleep apnea therapy for prevention of heart attack.”

“The study results are important because sleep apnea may affect as many as 20 million Americans,” notes lead study author Fatima Sert Kuniyoshi, PhD. “And even though the condition is common, it is underreported and undertreated.”

Further research is required to determine if treating sleep apnea will reduce the risk of heart attack and sudden death.

This study is published in the July 29th issue of the Journal of the American College of Cardiology.

Sources:

Sert Kuniyoshi F. et al. Day-Night Variation of Acute Myocardial Infarction in Obstructive Sleep Apnea. Journal of the American College of Cardiology, 2008.

Virend Somers, MD, PhD, Professor of Cardiovascular Diseases, Mayo Clinic and Foundation, Rochester, Minnesota.

Fatima H. Sert Kuniyoshi, PhD, Division of Cardiovascular Diseases, Mayo Clinic and Foundation, Rochester, Minnesota.

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