SALT LAKE CITY – Studies consistently show a link between obstructive sleep apnea and stroke, with the most recent data showing that sleep apnea is an independent risk factor for stroke and death.
The cumulative data in regard to sleep apnea and stroke suggest that patients with sleep apnea should be treated with continuous positive airway pressure (CPAP) or other measures, Dr. Vahid Mohsenin said at the annual meeting of the Associated Professional Sleep Societies.
The evidence supporting the efficacy of CPAP is overwhelming–with good compliance, efficacy is about 90%–and the expectation is that treatment will reduce the risk of stroke, although more research is needed to confirm this, said Dr. Mohsenin, professor of medicine and director of the Yale Center for Sleep Medicine, Yale University, New Haven, Conn.
In fact, a guideline from the American Heart Association/American Stroke Association Stroke Council for the primary prevention of ischemic stroke was updated earlier this year to incorporate new information about stroke prevention, including data on the role of sleep-disordered breathing in stroke. The guideline was initially published in 2001.
Although the guideline stops short of making specific treatment recommendations, and instead states that treatment should be individualized, it does address patient evaluation. It is reasonable that patients and their bed partners be questioned about symptoms of sleep-disordered breathing and that appropriate patients be referred to a sleep specialist for further evaluation, the guideline states.
This is particularly important if the patient has drug-resistant hypertension or certain risk factors for stroke, such as abdominal obesity and hypertension (Stroke 2006;37:1583–633).
In making its recommendation, the AHA/ASA Stroke Council cited data from several studies, including a case-control study of 181 patients, which showed an association between excessive daytime sleepiness (likely caused by obstructive sleep apnea) and stroke (odds ratio 3.07).
The council also cited a 10-year observational study of more than 1,600 men, which showed that those with severe obstructive sleep apnea-hypopnea had an increased risk of fatal and nonfatal cardiovascular events including stroke, compared with healthy individuals (OR 2.87 and 3.17, respectively).
The guideline noted that there are a number of biologically plausible mechanisms for a link between sleep apnea and stroke; Dr. Mohsenin agreed.
Several studies suggest that the mechanism by which sleep-disordered breathing increases stroke risk is by “leading to or worsening hypertension and heart disease and possibly by causing reductions in cerebral blood flow, altered cerebral autoregulation, impaired endothelial function, accelerated atherogenesis, hypercoagulability, inflammation, and paradoxical embolism in patients with patent foramen ovale,” the guideline states.
But the real question, Dr. Mohsenin said, is whether there is an independent association between sleep apnea and stroke, and a recent study on which he was an author shows that there is indeed such an association.
In the observational cohort study of 697 patients with obstructive sleep apnea and 325 controls (mean apnea-hypopnea index of 35 vs. 2 in the patients and controls, respectively), obstructive sleep apnea was found to have a statistically significant association with stroke or death (hazard ratio of 1.91) after adjustment for numerous factors, including age, sex, race, smoking status, alcohol consumption, body mass index, diabetes, hyperlipidemia, atrial fibrillation, and hypertension.
A trend analysis also showed a significant dose-response relationship between sleep apnea severity at baseline and development of a composite end point of stroke or death from any cause (N. Engl. J. Med. 2005;353:2034–41).
While randomized controlled trials are needed to firmly establish a causal link between sleep apnea and stroke–to “put the last nail in the coffin and say, 'ok, sleep apnea is indeed a cause of stroke in a high-risk patient population,'” as Dr. Mohsenin put it, the findings increasingly suggest this is the case. Also, sleep apnea occurs as commonly in transient ischemic attack as it does in stroke, further underscoring the need for sleep apnea treatment in affected patients, he noted.
Additionally, a number of studies have shown that sleep apnea is associated with worse functional outcomes in stroke patients, Dr. Mohsenin said.
Patients with stroke who have sleep apnea have been shown to have more delirium, depression, impaired functional capacity, longer rehabilitation time, and longer hospitalization, he said.
“Sleep apnea does affect the outcome of stroke,” he said, noting that in some studies these effects lasted out to 12 months.
Patients who have had a stroke should be evaluated for sleep disordered breathing, he advised.
In addition, patients using long-term CPAP should be reevaluated for residual symptoms of the disorder to ensure adequate treatment and compliance, he added.