Sleep might seem like the simplest of activities, but physiologically it’s a complex multistage process. Each sleep stage plays a role in getting our bodies and minds the rest and recuperation we require. One sleep stage, in particular, stands out—rapid eye movement (REM) sleep, which is recognized by the erratic back-and-forth eye movements that can be observed even behind the sleeper’s closed eyelids.
Researchers have found that REM sleep plays a pivotal role in our mental processing and most likely our health as well. But how much REM sleep do you need…how can you increase your REM sleep…and what is REM sleep behavior disorder? Bottom Line Personal asked sleep specialist Michael Breus, PhD, for details…
The Importance of REM Sleep
REM sleep is when mental restoration occurs…and when the brain transfers recent short-term memories to the brain’s temporal lobe where they can become long-term memories. REM sleep is like a night-shift filing clerk deciding which elements of the day’s data we should save for later. This process of shifting memories from short-term memory into long-term memory also seems to help us see information in new ways, opening the door to sudden “ah-ha” moments. When you go to bed worried about a problem but wake up and find you have a potential solution, that insight occurred during REM sleep.
REM sleep is when approximately 80% of dreaming occurs. The purpose of dreams remains a matter of debate, but there’s strong and growing evidence that they’re beneficial. Examples: A recent study by researchers at University of California-Irvine found that dreaming helps people process emotional memories—and that processing appears to be linked to the development of emotional resilience. Even nightmares seem to serve a useful function—feeling fear while dreaming leads to better reactions to potentially frightening situations that occur while we’re awake, according to a study by researchers at University of Geneva and University of Wisconsin.
There’s some evidence that having difficulty reaching REM sleep also might be linked to elevated Alzheimer’s rates, though the existing research on this subject is not yet conclusive.
What Happens During REM Sleep
The human body and mind are surprisingly active during REM sleep—your heart rate and blood pressure are higher than during other stages of sleep…a meaningful number of calories are burned…and your brain activity is remarkably similar to its activity when you are awake.
Yet, paradoxically, the body tends to appear almost completely inactive during REM sleep, with little or no movement aside from necessary functions such as breathing, the eye movements mentioned above and the occasional twitch. This lack of movement serves a protective function—most of the muscles are temporarily paralyzed during REM sleep to prevent the sleeper from acting out his/her dreams and injuring himself or his bedmate in the process.
Caution: When that paralysis doesn’t work properly, sleepers may physically and/or verbally act out their dreams. It’s difficult to say how common this is, because people who experience this typically are not aware that it has happened unless informed of it by a startled bedmate. In fact, many don’t believe their bedmates even after they’re told what happened.
This condition is called REM sleep behavior disorder (RBD), and it seems to be most common among people age 50 and up. It occasionally leads to injuries, such as when people hit their bedmates or fall out of bed. The greatest danger associated with RBD isn’t that someone will be injured as a result of REM sleep movements, but that it might be caused by a serious underlying health problem. In about one out of three cases, RBD later turns out to be an early symptom of a neurodegenerative disorder such as Parkinson’s disease or Lewy body dementia. If you think you have RBD, talk to a neurologist. Taking certain antidepressants also has been linked to RBD.
How to Increase REM Sleep
It takes time to achieve a meaningful amount of REM sleep each night. REM sleep is the final stage of the four-stage “sleep cycle.” Each of these sleep cycles is around 90 minutes in length. Most people experience five sleep cycles during a full night’s sleep, though younger people sometimes have six and older people sometimes have just four.
The amount of REM sleep people get per cycle varies, with hardly any REM sleep occurring during the first cycle of the night—perhaps as little as 30 to 180 seconds. Longer and longer REM stages occur during subsequent cycles. By the final sleep cycle of the night, the REM stage could last up to an hour.
This more-REM-sleep-later-in-the-night pattern means that when we get slightly less sleep than normal, we tend to get significantly less REM sleep than normal because we miss out on the night’s last-and-longest REM stage.
Some simple math suggests the amount of sleep we should target to avoid missing out on this critical final REM stage. The typical sleep cycle takes around 90 minutes and the typical person gets five cycles per night, so seven-and-a-half hours of sleep are required to complete the fifth and best REM stage. Ideally, that should be rounded up to eight hours because people don’t necessarily fall asleep as soon as they shut their eyes…and because 90 minutes per sleep cycle is just the average, not a figure that’s set in stone. Exception: Sleep cycles are dramatically different for babies. REM sleep is the initial sleep stage for infants up to age six months, and it accounts for around half of their total sleep time.
Anything that chronically disturbs someone’s sleep can cost them this last and longest REM stage, including snoring bedmates, nighttime bathroom trips, active pets in the bedroom and/or deficiencies of vitamin D, magnesium or iron. It’s worth taking all necessary steps to limit these disturbances.
Especially important: Avoid caffeine late in the day. Not only does late-day caffeine consumption make it more difficult to sleep, it’s also been shown to reduce the amount of REM sleep people get relative to their overall sleep duration. There’s research suggesting that nicotine use and/or alcohol consumption late in the day also can lead to loss of REM sleep.
For some people, taking certain SSRI antidepressants completely eliminates REM sleep, potentially for years. But for reasons that remain unclear, people who experience this SSRI-induced REM sleep loss seem not to suffer the negative consequences that normally would be associated with a lack of REM sleep. If the use of these antidepressants keeps someone from feeling suicidal and/or makes it easier to live his/her life, they’re worth taking despite their potential effect on REM sleep. And REM sleep appears to return when antidepressants are discontinued.
Important: Do not assume you’re not getting enough sleep because a wearable fitness tracker reports a sleep deficit. These trackers are not always accurate. The best gauge of whether you’re getting sufficient sleep is whether you wake feeling rested. Also: Whether or not you remember your dreams is not correlated to whether you’re getting sufficient REM sleep.
