Uncontrolled Sleep Apnea May Harm Brain Health, Study Finds

Dubai, United Arab Emirates (CNN) — Uncontrolled sleep apnea, a disorder in which people stop breathing for 10 seconds or more at a time several times a night, may harm brain health in the future, a new study suggests.

It is estimated that 936 million adults worldwide between the ages of 30 and 69 may suffer from obstructive sleep apnea, with an even greater number of people undiagnosed. If sleep apnea is severe and untreated, people have a threefold risk of dying from any cause.

The study showed that people with severe sleep apnea, who spent less time during deep sleep, also known as slow-wave sleep, had more damage to the brain’s white matter than people with slow-wave sleep.

White matter is the tissue that forms the connections between brain cells and the rest of the nervous system. When the brain is examined, small white spots, called white matter hyperdensities, show the extent of the damage.

Study co-author Dr. Diego Carvalho, a Mayo Clinic neurologist in Rochester, Minnesota, USA, said that for every 10% decrease in the time spent in deep sleep, there was an increase in white matter hyperintensity in the brain. , which is equivalent to the effect of someone 2.3 years older.

“The association with sleep apnea was only detected when we isolated severe cases, suggesting that mild to moderate sleep apnea may not be significantly associated with white matter changes,” he added.

But Carlvalho pointed out that there is no cure for such changes in the brain, saying: “We need to find ways to prevent them from occurring or limit their aggravation.”

Experts note that having more white matter hyperintensity can slow down the brain’s ability to process information, pay attention, and remember. Low levels of white matter have also been linked to mental health problems such as depression, anxiety, and irritability.

“Their findings are consistent with the literature suggesting that sleep, including slow-wave sleep, plays an important role in maintaining brain health,” said Kristin Knutson, a sleep specialist and associate professor of neurology and preventive medicine at Northwestern University’s Feinberg School of Medicine in Chicago. .

“We’ve also seen associations between poor sleep quality and high blood pressure, and high blood pressure can lead to brain damage or stroke,” added Knutson, who was not involved in the new research.

White matter damage

The study, published in the journal Neurology on Wednesday, looked at a group of 140 people participating in the Mayo Clinic Study of Aging. The participants, with an average age of 72, were all without dementia, had no cognitive impairment during testing, and underwent one of two types of magnetic resonance imaging (MRI) scans.

It was found that about 34% of the participants suffer from mild sleep apnea, 32% of them suffer from moderate sleep apnea, and 34% suffer from severe sleep apnea. With sleep apnea, oxygen decreases, and carbon dioxide levels, blood pressure, and heart rate rise, Carvalho said.

“All of these changes lead to increased inflammation in the body and brain, activation of stress hormones that raise our blood pressure, affect metabolism, and blood may become thicker,” he explained. He pointed out that “changes in blood vessels can lead to a stroke, and poor blood supply to the brain can cause nerve cell death or white matter dysfunction, which may ultimately contribute to cognitive decline.”

The study looked at two biomarkers of brain damage: an increase in white matter hyperdensity and changes in corpus callosum fractions anisotropy (genu FA), which measures the movement of water within the fibers that connect neurons in the brain.

Carvalho said, “The changes in the movement of water in the axes are linked to problems in their safety, which indicates damage to their structure.” “We have used this procedure to investigate early white matter abnormalities associated with vascular disease,” he continued.

Experts consider dementia caused by vascular diseases to be the second most common type of dementia after Alzheimer’s disease.

Carvalho explained that after identifying conditions that can influence brain changes, such as age, high blood pressure, and cholesterol, the study found that each 10% reduction in slow-wave sleep is equivalent to three years of aging. As measured in the cavernous capsule of partial anisotropy.

Carvalho noted that a white matter hyperdensity scan showed similar results. The brain of a patient who got only 5% of his total sleep during the study in either slow-wave or deep sleep appeared 4.6 years older in terms of white matter abnormalities, compared to a patient who got 25% of his sleep during slow-wave sleep.

Some degree of white matter damage is typical in middle age, due to repeated exposure to environmental challenges such as pollution, stress, and cardiovascular problems, to name a few. And a study developed in 2019 found that there was hyperintensity in the white matter in the brains of 45-year-olds.

Such changes in white matter have been associated with an increased risk of cognitive decline, as well as Alzheimer’s disease and related types of dementia. However, damage to the white matter does not guarantee serious mental decline, said Alzheimer’s researcher Dr. Richard Isaacson, a preventive neurologist at the Neurodegenerative Institute in Florida.

“Having white matter disease is not a good thing, but it’s hard to judge how clinically significant this is,” said Isaacson, who was not involved in the new study. “Less judgment means more, but that doesn’t always translate into clinical symptoms.”

Knutson points out that the study can only show an association, not a cause. Therefore, more studies are needed to understand the relationship between sleep apnea and changes in the brain.

“The lower proportion of slow wave sleep may be a result of interrupted sleep, particularly due to obstructive sleep apnea, or slow wave sleep itself may be important for cardiovascular and brain health,” she said.

Why is slow wave sleep important?

During the first and second stages of sleep, the body begins to slow its rhythm. This leads to the third stage, a slow-wave or deep sleep where the body literally restores itself on a cellular level, repairing damage from the challenges of the day, and consolidating memories into long-term storage.

Years of research have concluded that sleep, especially the deeper kind, boosts immune function.

Isaacson explained that slow-wave sleep is also the time when the body “cleans out garbage” from the brain, including beta-amyloid, which is one of the hallmarks of Alzheimer’s disease.

The US Centers for Disease Control and Control reports that deep sleep is one of the best predictors of sleep quality, because a person must usually get relatively uninterrupted sleep to achieve this. Because each sleep cycle is approximately 90 minutes long, most adults require seven or eight hours of relatively uninterrupted sleep to achieve restorative sleep.

However, people with sleep apnea can wake up dozens of times part way through the night while snoring or gasping for breath. The constant interruption makes it difficult to get enough deep sleep and transition into the final stage, called rapid eye movement or REM sleep, where dreams occur.

Studies have shown that losing REM sleep can lead to memory deficits and poor cognitive outcomes, as well as heart disease and other chronic diseases, and early death.