According to a recent study, people who suffer from sleep apnea and spend less time in deep sleep may be more likely to have brain biomarkers associated with a higher risk of stroke, Alzheimer’s disease, and cognitive decline. Neurology, the medical journal of the American Academy of Neurology, will be published online. The study does not establish whether sleep difficulties cause changes in the brain or vice versa. It only shows a relationship. The study looked at sleep factors and biomarkers of the health of the brain’s white matter.
The biomarkers measure how well the brain’s white matter is preserved, which is important for connecting different parts of the brain. One of the biomarkers, white matter hyperintensities, are small 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 axons, which form nerve fibers that connect nerve cells.
“These biomarkers are sensitive signs of early cerebrovascular disease,” said study author Diego Z. Carvalho, MD, MS, of the Mayo Clinic in Rochester, Minnesota, and a member of the American Academy of Neurology. “Finding that severe sleep apnea and reductions in slow-wave sleep are associated with these biomarkers is important because there is no cure for these changes in the brain, so we need to find ways to prevent them from happening or getting worse.” ”
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The study included 140 people with obstructive sleep apnea, with an average age of 73, who underwent brain scans and were studied overnight in a sleep lab. The participants did not have cognitive issues at the start of the study and did not develop dementia by the end of the study. A total of 34 percent had mild, 32 percent had moderate and 34 percent had severe sleep apnea.
The sleep study examined how much time people spent in slow-wave sleep, also known as non-REM stage 3 or deep sleep, and is 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 hyperintensity, similar to an aging effect of 2.3 years. The same deficit was also associated with decreased axonal integrity, similar to the effect of being three years old.
People with severe sleep apnea had higher amounts of white matter hyperintensity than those with mild or moderate sleep apnea. They also had reduced axonal integrity in the brain.
The researchers took into account age, gender and conditions that could affect the risk of brain changes, such as high blood pressure and high cholesterol.
“More research is needed to determine whether sleep issues affect these brain biomarkers or vice versa,” Carvalho said. “We also need to see whether sleep quality improvement or sleep apnea treatment strategies can affect the trajectories of these biomarkers.”
The split-night design of the sleep study limited this overall study. Participants’ sleep was observed and their sleep factors were measured until they met criteria for a diagnosis of obstructive sleep apnea, mostly in the first two to three hours of sleep. Then he got a positive airway pressure machine overnight. Therefore sleep measurement may not be representative of a full night’s sleep.