What is REM sleep and why is it important?

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Any sleep tracker will show you that sleep is far from a passive affair. And no stage of sleep demonstrates that better than rapid eye movement, or REM, commonly referred to as dream sleep.

“It’s also called paradoxical sleep or active sleep, because REM sleep is actually very close to wakefulness,” said Dr. Rajkumar Dasgupta, a sleep medicine and pulmonary specialist at the University of Southern California’s Keck School of Medicine.

Before scientists discovered REM sleep in the 1950s, it was not clear that much was happening in the brain at night. However, researchers today understand sleep to be a highly active process made up of many different types of rest – including REM, which in some ways doesn’t feel like rest at all.

While the body is usually “off” during REM sleep, the brain is very much “on”. It is generating vivid dreams, as well as synthesizing memories and knowledge. Scientists are still working to discover how this strange state of consciousness works.

“It’s fair to say that there is a lot left to learn about REM sleep,” said Dr. Dasgupta. But from what researchers do understand, REM is vital to our emotional health and brain function—and possibly our longevity, too.

Throughout the night, “we’re going in and out of this rhythmic, symphonic pattern of the different stages of sleep: Non-REM 1, 2, 3 and REM,” Said Rebecca Robbins, instructor in medicine at Harvard Medical School and an associate scientist in the division of sleep and circadian disorders at Brigham and Women’s Hospital.

As soon as you blink, you enter the first stage of non-REM. It lasts less than 10 minutes and is considered light sleep. As you move into the second stage of non-REM sleep, your breathing and heart rate slow and your muscles relax, where your body temperature drops and your brain waves slow. You then enter the third stage, known as deep sleep, when your body repairs your bones and muscles, strengthens your immune system, releases hormones and restores your energy. .

After that, REM sleep begins, and your heart rate, breathing, and brain activity all increase. Brain regions involved in processing emotions and sensory input (from your dream world) light up. Meanwhile, your brain paralyzes the muscles in your arms and legs, preventing you from realizing your dreams, Dr. Dasgupta explained.

Ideally, you go through the four stages in 90- to 110-minute cycles that repeat four to six times during a typical night. Then, after your last REM cycle, you wake up rested and alert, said Dr. Indira Gurubhagavatula, sleep specialist at Penn Medicine and associate professor of medicine at the VA Medical Center in Philadelphia.

If you’ve ever gone to bed upset about something and ended up noticeably less upset, it’s probably a result of the emotional processing and memory reconsolidation that occurs during REM. There’s evidence that your brain divorces memories from their emotional charge—removing the “sharp, painful edges” from life’s difficulties, says Matthew Walker, a professor of neuroscience and psychology and founder of the Center for Human Sleep Science and said the director. California, Berkeley. REM is “like a form of overnight therapy,” he said.

REM also makes us better learners. During this sleep phase, your brain consolidates neural connections made from the previous day’s experiences and integrates them into existing networks, Dr. Robbins said.

Dr Walker continued: “We take those new pieces of information and start collating them with our back catalog of stored information. It’s almost a form of informational alchemy.”

These novel connections also make us more creative, he said. “We wake up with a modified mind-wide web of associations” that help us solve problems. Researchers in Dr. Walker’s lab conducted a small study where people were woken from different stages of sleep and asked to solve anagram puzzles. They found that subjects who were awakened from REM sleep solved 32 percent more anagrams than subjects who were interrupted during non-REM sleep.

Then, of course, there’s dreaming: The vast majority of our vivid dreaming occurs during REM. Some experts suspect that dreams are a mere byproduct of REM sleep — the mental expression of neurological function. But others think they can help people process traumatic experiences, Dr. Walker said.

And although most physiological processes, such as bone and muscle tissue repair, occur during non-REM sleep stages, some hormonal changes occur when a person is in REM, Dr. Walker said, such as the release of testosterone (which peaks at the beginning of sleep, the first REM cycle).

Genetics and other factors can affect the amount of sleep you need, but most adults should aim for seven to nine hours each night, including about two hours of REM sleep, Dr. Gurubhagavatula said.

In general, you need less sleep as you age, including slightly less REM. But a chronic lack of REM sleep, no matter what your age, can deprive you of its psychological benefits, Dr. Dasgupta said. You may have more trouble learning, processing emotional experiences, or solving problems.

Dr. Anna Krieger, medical director of the Center for Sleep Medicine at Weill Cornell Medicine, said irregular REM sleep has also been linked to cognitive and mental health issues, such as slowed thinking and depression. very short REM, fragmented REM and REM sleep behavior disorder – where muscle paralysis fails to occur and people often physically make their dreams come true kick or punch – are associated with neurological issues, ranging from mild amnesia to dementia and Parkinson’s disease.

A 2020 study of more than 4,000 middle-aged and older adults found that each 5 percent reduction in REM sleep was associated with a 13 percent higher risk of dying from any cause over the next two decades. Sleep deprivation in general has been associated with death, but research shows that not getting enough REM sleep is “the strongest predictor of all stages,” Dr. Walker said.

Dr. Walker and other experts aren’t sure what to make of this connection between REM sleep and mortality. “I don’t think we understand REM sleep very well yet can say with certainty what mechanisms are at play,” he said. Or, as Dr. Gurubhagavatula said, if the lack of REM is actually causing the death.

Dr. Gurubhagwatula said that it is difficult to separate the signs of REM sleep loss from the signs of overall sleep loss. If you’re sleep-deprived, you’re probably REM-deprived.

However, certain behaviors in particular can compromise your REM sleep. “Going to bed late and then using an alarm clock to wake up reduces your sleep, which can put you at risk of REM sleep deprivation,” Dr. Gurubhagwatula said. This is because the longest REM periods often occur at the end of the night.

Doctor. Drinking alcohol before bed also “markably worsens your REM sleep,” Walker said, because the process of metabolizing alcohol produces compounds that affect sleep cycle regulation. What’s more, Dr. Gurubhagwatula explained, moderate and heavy drinkers have a higher risk of REM sleep behavior disorder.

Antidepressants can also reduce REM sleep or trigger REM sleep behavior disorder. And specific conditions — such as narcolepsy, obstructive sleep apnea and depression — can increase your risk of REM abnormalities, Dr. Dasgupta said. If you have one of these conditions and are experiencing sleep deprivation, seek guidance from a sleep specialist. With sleep apnea, for example, “the minute we start therapy, people often get REM rebound,” Dr. Dasgupta said.

Although recent research suggests that people may get slightly more REM sleep in the winter, It’s a modern myth that you can target a specific stage of sleep for improvement. “People want to manipulate sleep and have more in this particular phase, but the body doesn’t work that way,” Dr. Krieger said. The natural structure of sleep is something not to be tampered with but to be protected.

“The way to healthy REM sleep is to focus on getting healthy sleep, and let your brain do the rest,” Dr. Gurubhagwatula said.

Dr. Robbins said that waking up and going to sleep at the same times every day helps your brain and body know when they need to rest, which makes sleep more efficient. Other behaviors that help regulate your biological clock include setting consistent meal times and not eating too late, exercising regularly, getting morning sunlight, and avoiding blue light in the evening.

Be sure to follow other sleep hygiene best practices, says Dr. Gurubhagwatula, such as avoiding alcohol and stimulants like caffeine and nicotine (especially later in the day) and maintaining a sleep environment that is dark, quiet, and cool. Are. And don’t overlook the importance of a wind-down routine to help you move from action into a night of rest and recovery — including that bizarrely busy time your brain spends in REM.

Carolyn Todd is a freelance health journalist covering health, mental health and diabetes.

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