Making sure we’re getting enough hours sleep is a growing cultural obsession. This is for good reason: we know that a good night’s sleep is essential for maintaining our overall well-being, supporting growth, development and healthy brain function. Meanwhile, getting too little leaves you vulnerable to both physical and mental health problems, and can shave years off your life.
But, with 71 percent of people in the UK reportedly not getting the recommended seven to eight hours a night, many people find themselves feeling groggy and exhausted throughout the day. When it comes to fixing this, knowing how much sleep we should be getting is a good place to start. So, we asked some experts all the big questions about sleep: how much do we need, when and why.
We've all heard the rule of thumb that every adult needs roughly eight hours a night, but actually this isn't quite right. “Sleep needs are based on the individual, and there’s a range of what ‘normal’ looks like,” says Katie Fischer, a certified holistic sleep coach. Global studies have shown most people need somewhere between seven and nine hours sleep per night.
Yes, quantity is important, but so is sleep quality. Sleep occurs in cycles of 90 minutes, during which we encounter light sleep, deep sleep and the REM stage, each of which is essential to our overall health and wellbeing. “Historically, we've thought of non-REM sleep as being the stage of sleep that's important for restoration of function, for recovery, for regulation of immune function and growth,” says Guy Leschziner, professor of neurology and sleep medicine at King's College London and author of two books on sleep (The Nocturnal Brain and The Secret World Of Sleep). “It's thought that REM sleep is perhaps more important in certain aspects of learning and of regulation of emotion. It's likely that, actually, it is the balance of non-REM and REM sleep that is important for many of these functions.”
“How much sleep our bodies can generate and obtain is something that we don't necessarily have a huge amount of control over,” says Fischer. “Particularly for people who seem to cope well on less sleep, and arguably just don't need as much sleep to perform and be healthy, we see that it runs in families. So there seems to be a genetic component.” Gender might also play a part, with studies showing that women sleep a bit longer than men.
How long you’re sleeping is also determined by age. Teenagers, for example, will generally need more hours of sleep, but once we hit adulthood the hours we need to sleep remain pretty stable.
There are also factors which impact how much sleep you need which are in your control. “We would expect that if we're looking at elite endurance athletes, that they would need sleep and they would be able to sleep more than someone who lives quite a sedentary life,” says Fischer. So, if you’re looking to get more sleep, making sure you’re doing enough exercise could be a good place to start.
A recent study of more than two million adults in the US found that the average bedtime for Gen Z and millennials is getting earlier, shifting from 10.18pm in January 2023 to 10.06pm in January this year for those aged 18 to 34. Among Gen Z, in particular, there’s a growing preference for an earlier bedtime, with many reporting that they are now in bed by 9pm – or earlier.
While this might work for some, Fischer thinks it’s better not to try to force yourself to go to bed at 9pm if you’re not likely to be sleepy then. “You might be creating a sleep problem unnecessarily,” she says. “Often, when you have difficulty falling asleep for a number of nights, you can begin to anticipate that difficulty sleeping, and you can become anxious and restless.”
There’s another potential problem with getting an early bedtime. As Fischer points out, we generally need around three hours to digest and metabolise our food before we go to sleep. So if we’re consuming dinner and going to sleep an hour or so later, this will impact the quality of our sleep.
Ultimately, your bedtime will come down to what time you need to get up. But aligning these times with your body’s natural rhythm will boost the quality of your sleep. Each of us follows an internal 24-hour clock, known as the circadian rhythm, which tells us when to sleep and when to wake up.
This is influenced by many factors – light and temperature among them – but your chronotype also plays a role. Your chronotype is your body’s natural inclination to sleep and wake at a certain time and determines whether you are a morning lark, night owl or somewhere in between. If you know someone who naturally wakes up late and works best late at night, this is often because they're wired as such.
“If you sleep in sync with your internal body clock, the quality of your sleep will be better,” says Leschziner. “Living out of sync with your body clock, even if you are getting sufficient sleep, can have negative effects.”
Whatever time you get to bed, it’s important to stick to it. “People often find that when they maintain consistent sleep and that's the main focus, they get better quality sleep,” says Fischer. “They feel more restored and energised.” In fact, one recent study showed that sleep regularity is a stronger predictor of mortality risk than the duration. So, we’re better off focusing on getting to bed at the same time every night than obsessing over how many hours we’re getting.
Following your instincts is key to understanding how much sleep you need within the advised seven to nine hour limit. If you wake up feeling refreshed and ready to start the day, you're unlikely going to need much more or less.
Beyond this, there are a few things you can do. “Firstly, if you currently use an alarm and your alarm didn't go off tomorrow morning, would you sleep past that alarm?” asks Walker. “If the answer is yes, then it means that your brain is not yet done with the sleep that it needs. It still needs more.”
Dr Alanna Hare, a consultant in sleep and ventilation at Royal Brompton Hospital, also suggests establishing a routine and sticking to it. “If you are going to bed and getting up at a different time every night and getting variable amounts of sleep each night, it is impossible to know how much sleep you need,” she says. Pick a waking up time and work backwards from there to establish a fixed bedtime. As above, this should be seven to nine hours earlier. Stick to this routine for two weeks.
If you feel exhausted, gradually go to bed earlier. Likewise, if you find you’re unable to fall asleep within 30 minutes, gradually go to bed later. “Keep doing this until you find you are generally waking refreshed and able to comfortably get through your day. That is the amount of sleep you need!”