Sleep Apnea Makes Wee Hours Sudden-Death Time

Risk Highest From 10 p.m. to 6 a.m. for Obstructive Sleep Apnea Sufferers

March 23, 2005 -- Nightmare time comes in the wee hours of the morning for people with obstructive sleep apnea. But it's no dream: That's when they're at highest risk of sudden death.

For most people, sudden death from heart attack is least likely from midnight until 6 a.m. Obstructive sleep apnea turns this on its head, report Apoor S. Gami, MD, and colleagues of the Mayo Clinic in Rochester, Minn.

People with sleep apneasleep apnea stop breathing for 10 seconds or longer during sleep. These episodes may occur from five to 50 times an hour. Blockage of the nose, mouth, or throat causes obstructive sleep apnea. It's most common in obese people, when fatty tissues in the neck press down on the airway. As many as one in four Americans suffers from obstructive sleep apnea.

Cardiac Death Peaks During Night

Gami's team obtained death records for 112 Minnesota residents who had been treated at the Mayo Clinic sleep center and later died sudden, heart-related deaths.

For those without obstructive sleep apnea, sudden death was most likely to come in the daytime. But for obstructive sleep apnea patients, nighttime was the most deadly time of day. The study could not verify whether continuous positive airway pressure (CPAP) was used the in days before sudden death. The treatment helps people with obstructive sleep apnea breathe better.

"People with obstructive sleep apnea have a peak in sudden death from cardiac causes during the sleeping hours," Gami and colleagues write. Their findings appear in the March 24 issue of The New England Journal of Medicine.

That's not surprising. At night, people with untreated obstructive sleep apneaobstructive sleep apnea have too little oxygen and too much carbon dioxide in their blood. Their nervous systems are jumpy, their blood pressure surges, the walls of their hearts are stressed, and their heart rhythm is disturbed. Their blood clots easily and carries too many damaging free-radical compounds.

It also stands to reason that obstructive sleep apnea would increase a person's overall risk of sudden death. But the Gami study doesn't address this question.

"Given our findings and the relatively high prevalence of obstructive sleep apnea in Western populations, this is an important question that remains to be answered," Gami and colleagues write.

Show Sources

SOURCE: Gami, A.S. The New England Journal of Medicine, March 24, 2005; vol 352: pp 1206-1214.
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