Results of a large international study show stroke risk was more than three times higher in those who slept too little, more than twice as high in those who sleep too much, and two to three times higher in those with symptoms of severe obstructive sleep apnea.
The study also showed that the greater the number of sleep disorder symptoms, the greater the stroke risk. The 11% of study participants with five or more symptoms of disordered sleep had a fivefold increased risk for stroke.
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Although the study data do not show a causal link between disordered sleep and stroke, the association between the two was strong.
“Given the association, sleep disturbance may represent a marker of somebody at increased risk of stroke, and further interventional studies are required to see if management can reduce this risk,” lead investigator Christine McCarthy, MD, PhD, a geriatric and stroke medicine physician and researcher with the University of Galway (Ireland), told this news organization. “In the interim, however, management of sleep disturbance may have a positive impact on a patient’s quality of life.”
The findings were published online in the journal Neurology.
More symptoms, more risk
Previous research shows severe OSA doubles the risk of stroke and increases the chance of recurrent stroke. A 2019 study showed that people with insomnia had a small increased risk of stroke.
“Both snoring and extremes of sleep duration have been previously associated with an increased risk of stroke in observational research, but less is known about other symptoms of sleep impairment, with less consistent findings,” Dr. McCarthy said.
Prior studies have also generally come from a single geographic region, which Dr. McCarthy noted could limit their generalizability.
For this effort, investigators used data from 4,496 participants in INTERSTROKE, an international case-control study of risk factors for a first acute stroke. About half of the participants had a history of stroke.
Using information collected from a survey of sleep habits, researchers found an elevated stroke risk in those who received less than 5 hours of sleep per night (odds ratio, 3.15; 95% confidence interval, 2.09-4.76) or more than 9 hours of sleep per night (OR, 2.67; 95% CI, 1.89-3.78), compared with those who slept 7 hours a night.
Participants who took unplanned naps or naps lasting an hour or more (OR, 2.46; 95% CI, 1.69-3.57) and participants who reported poor quality sleep (OR,1.52; 95% CI, 1.32-1.75) were also at an increased risk for stroke.
Symptoms of OSA were also strongly associated with increased stroke risk, including snoring (OR, 1.91; 95% CI, 1.62-2.24), snorting (OR, 2.64; 95% CI, 2.17-3.20), and breathing cessation (OR, 2.87; 95% CI, 2.28-2.60).
Stroke risk increased as the number of sleep disturbance symptoms rose, with the greatest risk in the 11% of participants who had five or more symptoms (OR, 5.38; 95% CI, 4.03-7.18).
“This study finds an association between a broad range of sleep impairment symptoms and stroke, and a graded association with increasing symptoms, in an international setting,” Dr. McCarthy said.
Researchers aren’t sure what’s driving the higher stroke risk among people with sleep disturbances. Although the study did control for potential confounders, it wasn’t designed to get at what’s driving the association.
“Sleep disturbance may also have a bi-directional relationship with many stroke risk factors; for example, sleep disturbance may be a symptom of disease and exacerbate disease,” Dr. McCarthy said. “Future interventional studies are required to determine the true direction of the relationship.”