Sleep fragmentation may affect brain arteries and tissues.
Image credit: American Heart Association
As people age, they experience new sleep patterns. Insomnia creeps in and falling asleep takes longer. Sleep fragmentation, when sleep is interrupted by repeated awakenings or arousals, can also be a problem.
Changes that occur in circadian rhythms, the body clock that coordinates timing of bodily functions, including sleep, can cause older people to become sleepier in the early evening and to wake earlier in the morning.
Sleep problems can stem from an underlying medical or psychiatric condition, but they are also a risk factor for further health issues, including cardiovascular disease.
Poor sleep quality has been linked with more severe arteriolosclerosis in older people's brains and of higher levels of oxygen-starved brain tissue, or infarcts. These factors increase the risk of stroke and cognitive impairment.
In the current study, researchers wanted to see if there was an association between sleep fragmentation and detailed microscopic measures of blood vessel damage and infarcts in autopsied brain tissue from the same individuals.
Reduced supply of oxygen to the brain
The team, led by Dr. Andrew Lim, an assistant professor of neurology at the University of Toronto, Canada, examined autopsied brains of 315 people, of whom 70% were women; the average age was 90 years.
Participants had undergone at least 1 full week of around-the-clock monitoring for rest or activity, from which sleep quality and circadian rhythms were quantified. Sleep fragmentation caused sleep to be disrupted on average almost seven times each hour.
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.
Greater sleep fragmentation was associated with a 27% higher chance of having severe arteriolosclerosis. For every additional two arousals per hour of sleep, there was a 30% higher chance of having visible signs of oxygen deprivation in the brain.
Other cardiovascular risk factors, such as body mass index (BMI), smoking history, diabetes, hypertension and other medical conditions such as Alzheimer's disease, pain, depression or heart failure were all adjusted for.
Dr. Lim says:
"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. 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."
The findings suggest that sleep monitoring could help to identify seniors at risk of stroke, but further study is needed to clarify 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 are also unclear.
Medical News Today recently reported on research suggesting that people who lack sleep also have a tendency to eat or drink more while doing another activity, such as watching television.