A recent study focused on examining the correlation between sleep habits and the biomarkers associated with the health of the brain’s white matter. These biomarkers are essential in measuring the preservation of the brain’s white matter, which plays a significant role in connecting various regions of the brain. Among these biomarkers, white matter hyperintensities are small lesions that are visible in brain scans. These hyperintensities become more frequent as an individual ages or experiences uncontrolled high blood pressure. The other biomarker studied measures the integrity of the axons, which are responsible for forming 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 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.”
The study involved 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. A total of 34% had mild, 32% had moderate and 34% had severe sleep apnea.
The sleep study examined how long people spent in slow-wave sleep, which is also called 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 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.
The researchers accounted for age, sex and conditions that could affect risk of brain changes, such as high blood pressure and high cholesterol.
A study was conducted on 140 individuals with obstructive sleep apnea, averaging 73 years of age, who underwent a brain scan and an overnight sleep study. At the start of the study, participants did not have cognitive issues and did not develop dementia by its end. The severity of sleep apnea was mild, moderate, or severe in 34%, 32%, and 34%, respectively.
The sleep study focused on measuring slow-wave sleep, also known as non-REM stage 3, or deep sleep, which is considered the best indicator of sleep quality. The results showed that a 10-point decrease in the percentage of slow-wave sleep led to an increase in white matter hyperintensities, similar to aging 2.3 years, and reduced axonal integrity, similar to aging three years.
Individuals with severe sleep apnea had more white matter hyperintensities and reduced axonal integrity in their brain compared to those with mild or moderate sleep apnea. The researchers took into account factors such as age, sex, high blood pressure, and high cholesterol, which could impact the risk of brain changes.
“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.”
One limitation of the overall study was the split-night design of the sleep study. During the study, participants’ sleep was observed and their sleep factors measured until they met the criteria for obstructive sleep apnea diagnosis, which typically occurred within the first two to three hours of sleep. After that, they were provided with a positive airway pressure machine for the rest of the night. As a result, the recorded sleep measurements may not be fully representative of an entire night’s sleep.
