Obstructive sleep apnea can cause snoring, daytime sleepiness, and other health issues. Now, it has also been linked to damage to parts of the brain connected to memory, according to a study published in May in the Neurology^® journal. 

In obstructive sleep apnea, a person’s oxygen levels can drop while they sleep, as their throat muscles relax and block their airway. When this occurs, patients continuously awake in order to breathe, resulting in disrupted sleep. This can lower their oxygen levels and damage small blood vessels in their brains.

“Obstructive sleep apnea is a sleep disorder that increases with age, and low oxygen levels during sleep can harm the ability of our brain and body to function properly,” study author Bryce A. Mander, PhD, of the University of California, Irvine, said in a statement. “Our study found that low oxygen levels from obstructive sleep apnea, especially during REM [rapid eye movement] sleep, may be linked to cognitive decline due to damage to the small blood vessels in the brain and the downstream impact of this damage on parts of the brain associated with memory.”

REM is a critical stage of rest, as the body uses it to consolidate memories and process emotional experiences, and also is when most dreams happen.

Of the 37 people involved in the study, 24 had obstructive sleep apnea. The group was on average about 73 years old, and none were cognitively impaired or took sleep medications. They underwent a sleep study, had scans done to measure their brain structures, and took memory tests prior to and after sleep.

During each stage of sleep, researchers measured the participants’ oxygen levels, finding an association between lower oxygen levels during REM sleep and higher levels of white matter hyperintensities–bright spots visible on brain scans that can indicate damage to white matter tissue–in the brain. Damage to small blood vessels in the brain can cause these spots.

Researchers say two factors together predicted the number of white matter hyperintensities that appeared on participants’ scans: their minimum blood oxygen saturation level during sleep and the total time they were asleep with a blood oxygen level of less than 90 percent. (Blood oxygen levels below that threshold are cause for concern.)

Additionally, the study found the presence of more white matter hyperintensities was associated with reductions in the size of two brain structures associated with memory: the hippocampus and the entorhinal cortex. Memory test results showed that those changes in the entorhinal cortex also were linked to deficits in sleep-dependent memory.

“Taken together, our findings may partially explain how obstructive sleep apnea contributes to cognitive decline associated with aging and Alzheimer’s disease through the degeneration of brain regions that support memory consolidation during sleep,” Dr. Mander says.

Researchers did note, however, that the study consisted of mostly White and Asian people, so their results may not apply to people of other backgrounds.

People with obstructive sleep apnea have several treatment options, including a continuous positive airway pressure (CPAP) machine, which uses a mask to provide filtered, purified, pressurized room air to patients as they sleep. Similar machines include the bi-level PAP, which provides different pressures for inhalation and exhalation, and the auto CPAP, which self-regulates and provides varied pressure levels.

Patients also may find some relief by sleeping on their side, which helps keep their airways open. Other treatments include retainer-style devices that push the patient’s lower jaw forward and pull their tongue forward to keep the back of their throat open; special strips placed outside your nostrils that increase pressure in the airways to prevent them from collapsing; surgery to remove the tonsils and adenoids or the tonsils, uvula, and part of the soft palate; and a quarter-sized device implanted in the patient’s chest wall that connects to their chest muscles and the nerve controlling tongue movement.

For more information about treatments, symptoms, and more, visit our sleep apnea information hub.