Poor sleep quality has been associated with more severe arteriosclerosis in the brains of elderly people, as well as a greater burden of oxygen-starved tissue on the brain. The findings have been reported in the American Heart Association journal, Stroke.
This study is the first to look specifically for an association between sleep fragmentation and detailed microscopic measures of blood vessel damage and infarcts in autopsied brain tissue from the same individuals.
Researchers examined autopsied brains of 315 people (average age 90, 70% women) who had undergone at least one full week of around-the-clock monitoring for rest or activity, from which sleep quality and circadian rhythms were quantified. In all, 29% of the patients had suffered a stroke, while 61% had signs of moderate to severe damage to their blood vessels in the brain.
Researchers found that greater sleep fragmentation was associated with 27% higher odds of having severe arteriosclerosis. Moreover, for each additional two arousals during one hour of sleep, researchers reported a 30% increase in the odds that subjects had visible signs of oxygen deprivation in their brain.
These findings were independent of other cardiovascular risk factors, such as body mass, smoking history, diabetes, and hypertension, or other medical conditions such as Alzheimer’s disease, pain, depression or heart failure, researchers report.
“The forms of brain injury that we observed are important because they may not only contribute to the risk of stroke but also to chronic progressive cognitive and motor impairment,” said Andrew Lim, lead investigator, an assistant professor of neurology at the University of Toronto, and a neurologist and scientist at Sunnybrook Health Sciences Center, in Toronto, Canada.
“However, there are several ways to view these findings: sleep fragmentation may impair the circulation of blood to the brain, poor circulation of blood to the brain may cause sleep fragmentation, or both may be caused by another underlying risk factor,” he says.
The findings suggest that sleep monitoring may potentially be another way to identify seniors who may be at risk of stroke, but further work is needed to clarify several points: whether brain blood vessel damage is a consequence or a cause of sleep fragmentation; the role of specific contributors to sleep fragmentation such as sleep apnea and the underlying biological mechanisms.
Co-authors are Lei Yu, Julie Schneider, David Bennett, and Aron Buchman—all investigators at Rush University’s Alzheimers Disease Center and the Department of Neurological Sciences in Chicago, USA. Author disclosures are on the manuscript.
The National Institutes of Health, Canada’s Heart and Stroke Foundation, and the Canadian Institutes of Health Research supported the study.