What is REM Rebound Sleep?

Have you ever had a night where it seemed that you dreamt more than usual? You were probably experiencing a sleep stage increase known as REM rebound sleep. But what is REM rebound sleep exactly, and what is the cause? We’ll answer both of these questions and more as we explore this interesting sleep phenomenon.

But before we jump into REM rebound sleep, first we’ll go over the basics of regular REM sleep.

REM Sleep

Three are four stages in the sleep cycle: the first three are non-REM stage (NREM) sleep and the last is REM sleep (or rapid eye movement sleep). The NREM stages slowly coax you into a deep sleep before REM begins. The NREM sleep stages include three phases: 

• N1 is the light sleeping stage where you can be easily woken, but just start to drift off.
• N2 is where your heart rate slows, your eyes cease their movements, and your body temperature drops.
• N3 is the deep sleep stage. During N3, your body physically repairs itself, from the muscles and tissues, to immune function.

As you enter REM, about 70-90 minutes after you fall asleep, your brain becomes more active. This is the sleep stage where you begin to store memories, solve our waking problems, and some theorize that it helps improve mood.

Related: Stages of sleep

REM rebound sleep is characterized as an increased amount of REM sleep throughout the night compared to normal REM lengths and frequencies. REM makes up about 20% of the night’s sleep stages, but those experiencing REM rebound see about a 7% increase. So, why does REM rebound occur?

Causes of REM Rebound

Simply put, REM rebound is caused by REM sleep deprivation. When you miss those precious hours of sleep, your brain misses out on the amount of sleep cycles it needs—including REM sleep. Over time, as your body gets less REM sleep you start to build up REM sleep debt. So, when you finally lie down to rest, your body tries to make up for the REM deprivation by not only making this stage longer, but also more frequent.

With REM rebound, the first REM sleep period occurs soon after falling asleep rather than 70-90 minutes after. Every REM cycle after that is much longer than it would normally be. The dreams during these cycles are usually very vivid and intense. Sometimes they are so intense that dreamers are awoken suddenly, possibly to sleep paralysis.

Along with sleep deprivation, some antidepressants or selective serotonin reuptake inhibitors (SSRIs) can decrease REM sleep and increase REM latency. Other risk factors include substance abuse, drinking alcohol, and using CPAP treatment for sleep apnea treatment. 

REM Rebound and Alcohol

When you consume alcohol, it shortens your REM cycles during the early cycles of your sleep. Then, as your body metabolizes alcohol, you experience slight withdrawal symptoms. These include:

• Sleep disruption and frequent awakenings (which can lead to REM rebound)
• REM rebound
• Nightmares
• Insomnia (which can lead to REM rebound)

Though some use alcohol to help them fall asleep, it leads to a poor, less restorative night’s sleep in the end.

REM Rebound and Obstructive Sleep Apnea

Studies have shown that REM rebound is especially prevalent in people with sleep apnea—especially as they use CPAP treatment. A CPAP (continuous positive airway pressure) is a machine that helps OSA patients breathe as they sleep.

Those who use CPAP treatment for sleep apnea typically experience changes in their sleep architecture such as slow-wave sleep rebound, less sleep fragmentation, and REM rebound. In one 2017 study in particular, the results showed a 57% increase in REM sleep duration while patients used the CPAP. 

Is REM Rebound Dangerous?

It is important to remember that REM rebound is something everyone has probably experienced at one point or another; it is our brain’s way of making up for lost sleep. Researchers say that REM rebound sleep is not dangerous or harmful. In fact, sleep scientists are more puzzled and interested in REM rebound than anything.

However, there is such a thing as too much REM sleep. People who suffer from excessive REM sleep can feel tired and groggy the next day. This could be a sign of any number of sleep disorders, depression, or a bigger health issue. If you find that you are in REM sleep the majority of the night or that your sleep duration is more than 10 hours, it may be time to contact your doctor.

If you want to know exactly how much time you are spending in REM, there are ways to obtain this information. The easiest way is by using a sleep tracker. A sleep tracker collects data through movement, heart rate, and breath. They take these biometrics and turn them into easily digestible data (such as how long you spend in each sleep stage).

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Summary

REM rebound sleep is a deviation from your body’s natural sleep cycle. When you deprive yourself of sufficient REM sleep (either through sleep deprivation, substance withdrawal, or sleep apnea) your brain will make up for it by promoting extra and longer REM cycles. 

With your REM increased, you will experience more dreams that are vivid or nightmarish. Your body may wake itself up before the REM cycle is finished, causing sleep paralysis. Despite these side effects, REM rebound is completely normal and nothing to worry about.