What exactly is REM sleep and why do we need it?

If you use a wearable device to track your sleep habits, you’re probably familiar with the phrase “REM sleep”. But what is it and why is it important?

REM sleep goes by many names – dream sleep, active slumber and even paradoxical sleep (we’ll explain that one later).

So, what is it and why do we need it?

REM sleep occurs in cycles throughout the night, typically starting about 90 minutes after falling asleep.

During REM sleep, your brain activity, breathing, heart rate, and blood pressure all increase, and your eyes move rapidly while closed.

It’s distinctly different to slow wave sleep, the physically restorative stage of sleep that’s also known as deep sleep, when cells regenerate and your body repairs itself.

What happens during REM sleep?

University of Western Australia Centre for Sleep Science director and sleep physiologist Dr Jen Walsh says REM sleep is important for memory consolidation, emotional regulation and brain development.

“Newborns spend a lot of time in REM sleep because they’re developing their cortical pathways and processing all of the new things they’re experiencing,” Dr Walsh says.

Sleep Health Foundation CEO Dr Moira Junge says REM is when you tend to dream.

“Around 80 per cent of our dreaming occurs in REM,” Dr Junge says.

“It’s a very active stage where our heart rate increases and our muscles are switched off – that is, we have complete muscle atonia, like temporary muscle paralysis, which is thought to be protective so that we don’t physically act out our dreams.”

That’s where the term “paradoxical sleep” comes from.

Although our brains are totally active in REM sleep, we’re experiencing simultaneous muscle paralysis so we don’t hurt ourselves.

Fascinating, right?

How much REM sleep do we need?

In general, adults only require about two hours of REM sleep each night and, while multiple studies of humans and animals suggest that being deprived of sleep interferes with memory formation, the experts stress there’s no need for us to lose sleep if we’re not getting enough REM sleep.

“REM sleep is important but we can live without it,” Dr Walsh explains.

“People with certain sleep disorders live without it and people on certain medications live without a lot of it.”

Dr Junge adds that trying to engineer or manage how much REM sleep you get is futile.

Are “wearables” good for assessing sleep?

While many wearable devices, such as Apple, Garmin and Fitbit watches, now include sleep tracker functions, giving us intel on our daily sleep score (including how much time we’re spending in REM sleep), Dr Walsh warns they’re not always on target.

“Depending on the device and the individual using it, I’d say they’re about 70 to 80 per cent accurate,” she says.

Research, including a 2018 study from Oxford University, has also found that tracking sleep can have a negative psychological impact with some of us becoming more fixated with sleep.

Instead, our experts recommend, we should be thinking about sleep more holistically.

“There’s no need for people to specifically aim for more REM sleep over, say, more deep sleep; all stages of sleep are important and necessary and there is no way to specifically get more REM sleep,” Dr Junge says.

“Sleep experts would all say get better sleep quality and quantity – better sleep in general will improve the amount of REM sleep and all other stages of sleep.”

“Implementing good sleep hygiene and a good sleep schedule, where you’re getting a regular amount and getting up at the same time is what’s important,” Dr Walsh agrees.

Prioritising healthy sleep habits, creating an environment conducive to quality rest and nurturing your body clock could be just the REM-edy you need.

For more tips to improve your sleep:

Written by Liz McGrath.