The new review concludes that sleep problems can raise stroke risk and hinder patient recovery.
Around 50-70 million adults in the United States have some form of sleep disorder and, as a result, are at increased risk of health problems.
Study co-author Dr. Dirk M. Hermann, of University Hospital Essen, Germany, and colleagues note that previous research has suggested a link between sleep disorders and stroke risk and recovery.
In order to gain a better understanding of this association, the team conducted a meta-analysis of 29 studies that assessed how sleep disorders, such as insomnia and obstructive sleep apnea (OSA), may be associated with stroke and stroke recovery.
According to the Centers for Disease Control and Prevention (CDC), every year, stroke is responsible for almost 130,000 deaths in the U.S.
Ischemic stroke is the most common form, accounting for around 87 percent of all strokes. This occurs when blood flow to the brain is blocked. Hemorrhagic stroke arises when an artery in the brain ruptures or leaks.
TIA does not last as long as ischemic or hemorrhagic stroke - blood flow to the brain is normally blocked for less than 5 minutes - but it is considered a warning sign for major stroke; if untreated, more than a third of people who have a TIA go on to have an ischemic or hemorrhagic stroke within a year.
Stroke patients 'should be monitored for sleep disorders'
Dr. Hermann and colleagues note that sleep disorders can usually be categorized in one of two groups: sleep-disordered breathing (SDB) - such as OSA, where breathing repeatedly stops and starts during sleep - and sleep-wake disorders (SWD), such as insomnia, which reduces sleep duration.
In their review, the researchers found that SDB was present among 72 percent of ischemic stroke patients, 63 percent of hemorrhagic stroke patients, and 38 percent of TIA patients.
Many patients had SDB prior to experiencing stroke, the team found, suggesting that such sleep disorders increase stroke risk.
SDB was most severe for patients with ischemic or hemorrhagic stroke, and these disorders persisted during stroke recovery. However, the team notes that such problems improved with treatment, such as continuous positive airway pressure (CPAP), which provides the patient with a constant flow of air through the nasal passages during sleep.
Overall, the researchers conclude that the evidence to date strongly suggests that SDB increases the likelihood of stroke and, without treatment, can hamper stroke recovery.
The authors also found evidence to suggest that SWDs - including insomnia, restless leg syndrome, and hypersomnia - increase stroke risk and harm stroke recovery, though they note that such evidence was weaker than for SDB.
While the study does not pinpoint the exact mechanisms by which sleep disorders may lead to stroke and hinder recovery, Dr. Hermann told Medical News Today about one possible pathway.
"Sleep has important restorative functions in the brain," he explained. "Sleep enables neuronal plasticity processes, which are required for stroke recovery."
Based on the evidence, the researchers believe individuals who have had a stroke should be monitored for sleep disorders.
"Although sleep disorders are common after a stroke, very few stroke patients are tested for them. The results of our review show that should change, as people with sleep disorders may be more likely to have another stroke or other negative outcomes than people without sleep problems, such as having to go to a nursing home after leaving the hospital."
Dr. Dirk M. Hermann
While there are a number of drugs that are available for sleep disorders, the research team is cautious to recommend them for stroke patients, due to insufficient evidence of their safety in this population.