Heart Conditions and Sleep Apnea





The following link and quoted May 23, 2005, article is from Science Daily, source of article, the American Thoracic Society
Moderate to Severe Sleep Apnea Significantly Raises Stroke Risk, Study Finds

Moderate To Severe Sleep Apnea Significantly Raises Stroke Risk, Study Finds


SAN DIEGO-Moderate to severe cases of the nighttime breathing problem known as obstructive sleep apnea significantly increases the risk of suffering a stroke, according to a study to be presented at the American Thoracic Society International Conference on May 23.

The study of 1,475 people found that those with moderate to severe sleep apnea at the beginning of the study were 3 to 4 times more likely to have a stroke than a comparable group of patients without sleep apnea during the next four years.

The study did not find any significant increase in the odds of having a stroke for people with mild sleep apnea compared with people without sleep apnea.
"The stroke risk we found for people with moderate to severe sleep apnea is quite significant-double the risk of other well-known risk factors for stroke, such as hypertension or diabetes," said senior researcher Douglas Bradley, M.D., Professor of Medicine and Director of the Centre for Sleep Medicine and Circadian Biology at the University of Toronto. He and colleagues Michael Arzt, M.D., and Terry Young, Ph.D., found that the risk of stroke was significant even after other risk factors for stroke, such as high blood pressure and obesity, were taken into account.

In obstructive sleep apnea, a person's airways narrows, or totally collapses, during sleep. As a result, a person stops breathing briefly multiple times throughout the night. The person's sleep is interrupted often, which may cause excessive daytime sleepiness or even high blood pressure.

The patients in the study were defined as having moderate to severe obstructive sleep apnea if their breathing stopped or slowed at least 20 times per hour of sleep. People whose breathing stopped or slowed between 5 and 20 times per hour of sleep were considered to have mild sleep apnea.

One reason obstructive sleep apnea may increase stroke risk is that it has been shown to cause high blood pressure, which is the most common risk factor for stroke, Dr. Bradley said. Another possible reason is that when a person stops breathing, the lack of oxygen kicks in the body's "fight or flight" response. Part of that reaction is to make the blood more clottable, and blood clots in the brain can cause a stroke.

"This study provides yet another reason why it's important to treat sleep apnea," Dr. Bradley said. "It also raises the question of whether people with sleep apnea should be put on aspirin therapy or given other anti-clotting drugs, which is what is done for other people with stroke risk. This is an issue that needs further research."


The following link and abstract is from the November 10, 2005, article of the New England Journal of Medicine
Obstructive Sleep Apnea as a Risk Factor for Stroke and Death

Obstructive Sleep Apnea as a Risk Factor for Stroke and Death


Abstract
Background Previous studies have suggested that the obstructive sleep apnea syndrome may be an important risk factor for stroke. It has not been determined, however, whether the syndrome is independently related to the risk of stroke or death from any cause after adjustment for other risk factors, including hypertension.

Methods In this observational cohort study, consecutive patients underwent polysomnography, and subsequent events (strokes and deaths) were verified. The diagnosis of the obstructive sleep apnea syndrome was based on an apnea–hypopnea index of 5 or higher (five or more events per hour); patients with an apnea–hypopnea index of less than 5 served as the comparison group. Proportional-hazards analysis was used to determine the independent effect of the obstructive sleep apnea syndrome on the composite outcome of stroke or death from any cause.

Results Among 1022 enrolled patients, 697 (68 percent) had the obstructive sleep apnea syndrome. At baseline, the mean apnea–hypopnea index in the patients with the syndrome was 35, as compared with a mean apnea–hypopnea index of 2 in the comparison group. In an unadjusted analysis, the obstructive sleep apnea syndrome was associated with stroke or death from any cause (hazard ratio, 2.24; 95 percent confidence interval, 1.30 to 3.86; P=0.004). After adjustment for age, sex, race, smoking status, alcohol-consumption status, body-mass index, and the presence or absence of diabetes mellitus, hyperlipidemia, atrial fibrillation, and hypertension, the obstructive sleep apnea syndrome retained a statistically significant association with stroke or death (hazard ratio, 1.97; 95 percent confidence interval, 1.12 to 3.48; P=0.01). In a trend analysis, increased severity of sleep apnea at baseline was associated with an increased risk of the development of the composite end point (P=0.005).

Conclusions The obstructive sleep apnea syndrome significantly increases the risk of stroke or death from any cause, and the increase is independent of other risk factors, including hypertension.