Having sleep apnea and spending less time in deep sleep has been linked to developing brain biomarkers associated with an increased risk of stroke, Alzheimer’s disease and cognitive decline, according to a new research.
Researchers involved in the study said that it did not prove these sleep disturbances to cause the changes in the brain, or vice versa, but only that there was an association.
They have published their study in the journal Neurology. The study looked at sleep factors and biomarkers measuring of the health of the brain’s white matter, which is important to connect different parts of the brain. One of the biomarkers, white matter hyperintensities, are tiny lesions visible on brain scans. White matter hyperintensities become more common with age or with uncontrolled high blood pressure.
The other biomarker measures the integrity of the axons, which form the nerve fibers that connect nerve cells. “These biomarkers are sensitive signs of early cerebrovascular disease,” said study author Diego Z. Carvalho, of the Mayo Clinic in Rochester, Minnesota, and a member of the American Academy of Neurology.
“Finding that severe sleep apnea and a reduction in slow-wave sleep are associated with these biomarkers is important since there is no treatment for these changes in the brain, so we need to find ways to prevent them from happening or getting worse,” said Carvalho. The researchers studied 140 people with obstructive sleep apnea with an average age of 73 who had a brain scan and also an overnight study in a sleep lab. The participants did not have cognitive issues at the start of the study and had not developed dementia by the end of the study, they said.
A total of 34 per cent had mild, 32 per cent had moderate and 34 per cent had severe sleep apnea. The sleep study examined the time people spent in slow-wave sleep, which is also called non-REM stage 3, or deep sleep, and considered one of the best markers of sleep quality. The researchers found that for every 10-point decrease in the percentage of slow-wave sleep, there was an increase in the amount of white matter hyperintensities similar to the effect of being 2.3 years older.
The same decrease was also associated with reduced axonal integrity similar to the effect of being three years older. People with severe sleep apnea had a higher volume of white matter hyperintensities than those with mild or moderate sleep apnea. They also had reduced axonal integrity in the brain.
“More research is needed to determine whether sleep issues affect these brain biomarkers or vice versa,” Carvalho said. “We also need to look at whether strategies to improve sleep quality or treatment of sleep apnea can affect the trajectory of these biomarkers.”
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