Do you need to sleep through the night? Rethinking a perfect night’s sleep

A perfect night’s sleep is very individual. To a giraffe, one-to-two hours of sleep a night will hit the spot whereas a lion or armadillo need up to 20 hours a day.

So-called “elite” sleepers are an extremely rare breed of human – less than 1 per cent – whose genetic make-up allows them to feel refreshed after just four hours of sleep. Many who claim they function well off little sleep are simply “bravado types” who will suffer the consequences, says Ron Grunstein, the head of the Sleep and Circadian Research Group at the Woolcock Institute of Medical Research.

Most adults need somewhere between seven and nine hours a night to function optimally. But that seven to nine hours might not look the same for everyone.

Ask the ancient Egyptians, and they would tell you that the best night’s sleep is split into two parts.

“The rich Egyptians got up in the middle of the night when it was cooler and had social hours,” says Associate Professor Delwyn Bartlett, a sleep specialist from the Woolcock Institute of Medical Research and the University of Sydney. “They’d often even have a party … somewhere between 3 and 5am.”

Our ancestors didn’t sleep in one chunk either. They typically rose once at night to attend to visitors and animals or start cooking their food for the morning.

Today, Mediterranean cultures still often split their sleep in two (biphasic sleep) opting for a five-hour block overnight and a two-to-three hour siesta in the afternoon. Some suggest the “siesta culture” is the most natural way for humans to sleep, a claim supported by research of 23,681 Greek adults that found those who quit their afternoon nap had a 37 per cent increased risk of cardiovascular disease after six years (perhaps because it is a “stress-releasing activity”, the researchers suggest).

But, this is not everyone’s cup of tea. One 2015 study, following hunter-gatherer communities in Africa and South America found a “striking uniformity” to sleep patterns across the groups despite their geographic isolation from each other. They tended to go to bed a few hours after dusk, sleep for about seven hours on average and rise just before or just after dawn. They rarely napped, had no equivalent word for insomnia and were typically in much better health than their industrialised counterparts.

Whether people in Western cultures sleep in one block (monophasic sleep) because it is best for our bodies or because it better aligns with our social rhythms is arguable, but either way, we don’t sleep the whole night through.

“We go through these one-and-a-half hour sleep cycles,” explains Sleep Health Foundation’s Moira Junge. “When we come out of these cycles it’s like a wake state that most of us don’t remember: we just go straight back down again and in the morning we’ll report that we slept all night.”

Reframing our expectations around sleep is an important first step because waking during the night is perfectly natural, says Bartlett.

“We only spend 20 per cent of the night in deep sleep and as we age that 20 per cent is diminished.”

The reason we spend most of the night in relatively light sleep is likely to be evolutionary, she explains. “When we were cave-dwellers, if we weren’t checking our environment regularly then the sabre-toothed lion might have come and eaten us up.”

What then is a perfect night’s sleep?

It depends largely on how well you feel and function the next day, says Grunstein.

“Sleep is not an ‘all or nothing’ phenomenon,” he says. “In everyone there are parts of the brain that are awake.”

For example, the auditory cortex of a newborn’s parents tends to remain awake, alert to their baby crying.

And when we stay in a new place, like a hotel, one hemisphere of the brain remains on night watch, at least for the first night or two.

What this all means is that two people can sleep for the same amount of time, but have different sleep quality depending on how much of their brain remained “awake”, Grunstein explains.

Regardless, there is a commonality across cultures: the total amount of quality sleep needed every 24 hours.

“We only spend 20 per cent of the night in deep sleep and as we age that 20 per cent is diminished.”

Moira Junge, Sleep Health Foundation

How we achieve that comes down to a variety of factors that include what we’ve eaten or drunk before bed, our caffeine levels and our physical activity during the day. Our chronotype also affects the rhythm and timing of our sleep.

Here are four other ways to get a great night’s sleep:

Rage against the machine

One obvious contributor to great sleep is making enough time for it. This can be easier said than done when streaming services autoplay the next episode and social media lures us down rabbit holes. Suddenly, it’s midnight and we have to be up in six hours. So it’s essential to ensure we have somewhere between 7½ and 9½ hours in bed – in a dark, uncluttered room – to allow time to fall asleep and then get enough sleep.

Be regular but not exacting

Experts generally agree that regular sleeping hours help anchor our bodies to a rhythm.

“If you go to bed at the same time, it doesn’t guarantee you’ll sleep well but if you get up at the same time it does guarantee the end of your sleep period and your brain and body respond to that,” Bartlett says.

And although a regular wake-up time is helpful, it doesn’t have to be exact.

“If you’re going to have a little bit of a sleep-in, do it on a Saturday,” she suggests.” If you’re working Monday-to-Friday then Sunday needs to be a mid-point between a little sleep-in and the time you have to get up on a Monday.”

This, she says, allows us to enjoy a little extra sleep over the weekend but provides a gentle reset so we’re not jet-lagged throughout the week.

Synchronise yourself

Light exposure can either help align our bodies with the environment or misalign them.

Two hours before our regular wake-up time, our body temperature drops to its lowest point. If we have light before our minimum core body temperature – by checking our phones or tablets or turning on bright lights when we go to the bathroom during the night it lengthens our sleep-wake period. This means our body clock starts running longer than 24 hours, putting us out of whack with our external environment, which can leave us feeling permanently jet-lagged.

“If you’re going to have a little bit of a sleep-in, do it on a Saturday.”

Delwyn Bartlett, University of Sydney

“So what we need to do daily, is reset our sleep-wake cycle with our environment,” Bartlett explains.

Exposure to light after our minimum core body temperature sets our sleep-wake cycle so that it matches that of our environment. So if we wake at 7am, ensure the room is completely dark from the time we go to bed until at least 5am. And then, when we wake, view sunlight for a few minutes and, if we can’t be outside, turn on the lights to signal to our body it is time to wake up.

We can use this information to prepare for time differences when travelling. So light viewed in the hour or two before our minimum core temperature will make us want to go to sleep later and wake up later. Light viewed after our temperature minimum (but before we normally wake up) will make us want to go to sleep earlier, and wake up earlier. In the days before travelling to a new time-zone, we can gradually shift our body clock towards the destination’s time.

Get out of survival mode

Another significant piece of the puzzle is stress. If it is bubbling over into our sleep time, it renders any sleep challenging.

“It’s very hard for us to rest easy and sleep well if we’re under threat,” says Moira Junge.

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Making sure we are actively managing our stress levels when we are awake then is fundamental to our ability to rest easy at night.

Sleep take home: A perfect night’s sleep doesn’t look the same for everyone, but most of us need between seven-and-a-half and nine-and-a-half hours over every 24-hour period. Use how well you feel and function as a guide.

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