What To Know About REM Sleep & How Much Time To Spend In It Each Night

REM (rapid-eye movement) sleep is one of four stages that we move between throughout sleep (the others are Stage 1, Stage 2, and Stage 3, or deep sleep).

When we're in REM sleep1, our eyes begin to move quickly behind the eyelids, our brainwaves speed up, our temperature fluctuates, and our muscle activity is suppressed. It's also one (but not the only) sleep stage in which we dream. Since REM mimics wakefulness in certain ways, some scientists prefer to call it "active sleep."

Jerome Siegel, Ph.D., a professor of psychiatry at UCLA, notes that REM—while important—is just one component of the larger sleep picture. "I don't think you can separate REM sleep and sleep in general," he tells mindbodygreen.

This means that it's important to make sure you're getting enough total sleep each night before you worry too much about time spent in REM vs. non-REM.

With this in mind, researchers have found2 that the first stage of REM sleep typically starts about 60 to 90 minutes after we fall asleep, and it lasts around 10 minutes. As the night goes on, we phase in and out of REM cycles, and the time spent in each gets longer and longer. The last stage of REM can get up to an hour in length, so most of our REM time happens during the back half of our sleep.

The amount of time we spend in REM will vary depending on our age, with babies typically spending more time in this sleep stage5 than older adults. But generally, Girardin Jean-Louis, Ph.D., professor of population health and psychiatry at New York University previously told mbg, "Healthy sleepers might spend approximately 20% of their sleep time in the REM sleep stage." Given that most people need between seven and eight hours of sleep a night, that means around 90 minutes of REM sleep a night will be a sweet spot. But again, it depends on the person and their unique sleep needs.

We all know that getting too little sleep is not healthy, but what about too much? "There is an optimal amount of sleep, just like there is for many other physiological functions," says Siegel, who for the sake of this example likens sleep to blood pressure: You don't want it to be too low, but you don't want it to be too high either.

"The epidemiology7 indicates that there's an optimal amount of sleep—about seven hours, eight hours for most people—but people who sleep longer than that actually do worse than people who sleep less than that," he notes.

One reason could be that going against your body's natural sleep-wake cycle—either by sleeping too much or too little—throws off your circadian rhythm, explains integrative medicine physician Dana Cohen, M.D. So if you spend your morning snoozing in REM during a time when your body increases levels of energizing hormones like cortisol, it could throw off your hormonal balance, which has downstream effects.

Low mood, anxiousness, and other health concerns could all lead somebody to oversleep. Oversleeping also seems to be bidirectional, meaning that somebody may sleep too much because they're stressed, and then oversleeping makes their stress worse.

If you suspect that you're oversleeping or spending too much time in REM, using an at-home sleep tracker can help you get a better sense of your sleep habits. However, these only roughly estimate the amount of time you spend in each sleep stage, so Cohen recommends seeing a doctor for a proper polysomnography (PSG) sleep study to get to the bottom of it and rule out any sleep disorders.