Sleep apnea increases stroke risk

Stroke is the second leading cause of death worldwide and a leading cause of long-term disability. New research shows that obstructive sleep apnea (OSA), which often goes undiagnosed, is associated with an increased risk of stroke in middle-aged and older adults.

Sleep apnea is a disorder in which a person has one or more pauses in breathing or shallow breaths while he or she sleeps. Breathing pauses typically last longer than 10 seconds and occur 10–20 times or more an hour. Breathing may resume with a loud snort, choking sounds, or snoring. Sleep apnea is a widespread health problem; almost half of adults report snoring, which is a common sign of sleep apnea. The new research shows that even mild sleep apnea increases the risk of stroke, especially in men.

What was the study?

The study, "Obstructive Sleep Apnea-Hypopnea and Incident Stroke: The Sleep Heart Health Study," was funded by the National Heart, Lung, and Blood Institute (NHLBI). Results were published in the American Journal of Respiratory and Critical Care Medicine, July 15, 2010.

• 5,422 participants (2,462 men and 2,960 women) aged 40 years and older were part of the Sleep Heart Health Study, a community-based study of the cardiovascular consequences of OSA in a diverse population.
• Researchers asked participants about their sleep habits, general health, and medication use. At the start of the study they had no history of stroke and were untreated for sleep apnea.
• The presence and severity of sleep apnea were determined with an at-home sleep test (overnight unattended polysomnography). Researchers defined obstructive apnea-hypopnea index (OAHI), a measure of OSA severity, as the average number of obstructive apneas and hypopneas per hour of sleep.
• Participants were followed for a median of almost 9 years. Incidence of ischemic stroke was determined by direct participant contact as well as by surveying death certificates and discharge information from local hospitals.

What did the study find?

• During the study period, 193 participants had an ischemic stroke (85 men and 108 women). This is an estimated incidence rate of 4.4 strokes per 1,000 person years. 
• A strong dose-dependent association was found between ischemic stroke and OSA in men with mild to moderate sleep apnea; there was an increase in stroke risk as OSA severity increased.
• Ischemic stroke was three times more likely in men with untreated OSA, compared with men with mild or no OSA.
• The relationship between stroke risk and OSA was not explained by adjustments for weight, high blood pressure, race, smoking status, and diabetes.
• In women, stroke risk increased only in the category of highest OSA severity.

What are the take-home messages?

• OSA is associated with an increased risk of stroke, particularly in middle-aged men. Stroke risk increases with even mild sleep apnea signs and symptoms and increases with apnea severity.
• OSA is a common disorder. Signs and symptoms may include:
• Frequent loud snoring
• Pauses in breathing during sleep
• Awakening with a sensation of choking or gasping
• Excessive daytime sleepiness
• Morning headaches
• Memory or learning problems, difficulty concentrating
• Irritability, depression, mood swings, or personality changes
• Urination at night (nocturia)
• A dry throat upon waking
• Although OSA is more common among overweight, obese, and elderly patients, this breathing disorder can develop in otherwise healthy men, women, and children of any age.
• Health professionals should consider asking patients about the quality of their sleep. Further evaluation by a sleep disorder specialist may be warranted in patients who report signs and symptoms of sleep disordered breathing.
• People who have signs and symptoms of sleep apnea or feel burdened by excessive daytime sleepiness should consult their health care provider for advice.
• Stroke is a leading cause of death in the United States. In addition to OSA, other risk factors for stroke that people can control include high blood pressure, smoking, diabetes, and heart disease. 

Where can I learn more?

• Redline, S., Yenokyan, G., Gottlieb, D., Punjabi, N.M. (2010). Obstructive Sleep Apnea-Hypopnea and Incident Stroke: The Sleep Heart Health Study.  American Journal of Respiratory and Critical Care Medicine, 182:269–277.
• "Sleep Apnea" from the NHLBI Diseases and Conditions Index (DCI)
• "Stroke" from the NHLBI DCI
• Sleep Heart Health Study (SHHS)
• Sleep Apnea Tied to Increased Risk of Stroke (News release)
• Clinical trials on sleep

March 2011