Sleep disruptions in your 30s and 40s linked to cognitive decline a decade later, study finds

People who have the most sleep disruptions in their 30s and 40s are more than twice as likely to have memory and thinking problems a decade later, according to a new study.

In the early 2000s, researchers tracked the sleep quality of hundreds of people during two nightly visits about a year apart, capturing a total of six nights of sleep per person. Sleep quality was assessed using a wrist-based activity monitor that tracked the amount of sleep people got along with periods of movement to measure sleep fragmentation or brief, repetitive interruptions to sleep. Participants were about 40 years old, on average, at this time of the study.

More than a decade later, between 2015 and 2016, researchers analyzed the cognitive ability of 526 of the same participants using standardized interviews and tests of cognitive ability, including processing speed, executive function, memory, and fluency.

On average, study participants were found to sleep about six hours each night and about a fifth of their sleep time was interrupted. Overall, people who experienced greater sleep fragmentation, or who spent a greater proportion of their sleep hours moving, were more likely to receive poor cognitive scores on all tests more than a decade later.

Of the 175 people with the most disrupted sleep, 44 had poor cognitive performance 10 years later, compared to 10 of the 176 people with the least disrupted sleep, the study found.

The research was published Wednesday in Neurology, the medical journal of the American Academy of Neurology.

People who slept less or had greater sleep fragmentation were significantly more likely to be male, black, have a higher BMI, and have a history of depression or hypertension.

Due to the small sample size, the researchers were not able to fully investigate possible racial or gender differences. But after adjusting for health factors and other demographic data, people with the most disrupted sleep were found to be more than twice as likely to score worse than average on the set of cognitive tests compared to those with the most disrupted sleep. less interrupted.

“Since signs of Alzheimer’s disease begin to accumulate in the brain several decades before symptoms begin, understanding the connection between sleep and cognition earlier in life is critical to understanding the role of sleep problems as a risk factor for the disease,” study author Dr. Yue Leng, an associate professor of psychiatry at the University of California, San Francisco, said in a news release.

Throughout the study, participants were also asked to keep a sleep diary, recording their bedtime and wake-up times and assessing their own sleep quality. However, objective measures of sleep duration and subjective assessments of sleep quality did not correlate with cognition in midlife.

“Our findings indicate that sleep quality, rather than quantity, is more important for cognitive health in midlife,” Leng said.

People are supposed to sleep between seven and ten hours each night, depending on their age. But 1 in 3 Americans don’t get enough, according to the U.S. Centers for Disease Control and Prevention.

Additionally, between 50 and 70 million Americans struggle with sleep disorders such as sleep apnea, insomnia, and restless legs syndrome, which can ruin a good night’s sleep.

The CDC calls it a “public health problem” because sleep disruption is associated with an increased risk of diseases such as diabetes, stroke, cardiovascular disease and dementia.

A 2021 study found that people who reported routinely having difficulty falling asleep had a 49% increased risk of dementia, while those who woke up frequently during the night and had difficulty returning to sleep had a 39% increased risk of dementia. % increased risk of dementia. And a study published in October found that chronic loss of slow-wave sleep (the third stage of sleep, during which the body removes unwanted or potentially harmful materials from the brain) may increase the risk of dementia.

“More research is needed to evaluate the link between sleep disorders and cognition at different stages of life and to identify whether there are critical periods of life when sleep is most strongly associated with cognition,” Leng said. “Future studies could open up new opportunities for preventing Alzheimer’s disease in the future.”

The study used a wrist monitor to assess sleep fragmentation, Leng told CNN by email. He noted that there are consumer wrist trackers available, such as the Apple Watch and Fitbit, while Junxin Li of Johns Hopkins, an associate professor who studies sleep and cognitive function, added that there are others, including Garmin, Oura Ring and Dreem Band. .

However, assessment of sleep fragmentation in particular, which can involve “microawakenings” that a person may not even be aware of, is best done using electroencephalography or EEG monitoring, said Dr. Maggie Soltis, assistant professor of neurology and sleep medicine at Duke University. . However, she noted that that “can cause sleep fragmentation itself because now you’re trying to sleep with a bunch of electrodes on your head trying to monitor your brain wave activity.”

Commercially available trackers, he said, can be useful for observing trends.

The best way to address fragmented sleep, experts said, is to try to identify the cause.

“If the fragmentation is due to sleep disorders such as sleep apnea or restless legs syndrome, professional help is needed,” Li said.

To improve overall sleep, she recommended exercising regularly during the day, avoiding exercise close to bedtime, establishing a relaxing bedtime routine, reducing screen time in the evening, and avoiding large meals. , caffeine, nicotine and alcohol at night.

It’s also important to sleep in a cool, dark, quiet room, and try to wake up at the same time every day, Soltis added.

“However, if you have an underlying sleep disorder, these sleep hygiene recommendations are probably not enough to address the larger problem,” Soltis said. “That’s why I think talking to your doctor would be the most helpful (specifically making an appointment to focus and discuss sleep).”


CNN’s Meg Tirrell, Sandee LaMotte and Kristen Rogers contributed to this report.

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