Dr David Lee, Clinical Director at Sleep Unlimited, and author of Teaching The World To Sleep, says you should treat your bedroom as your nighttime sanctuary. “The golden rule is: save the bedroom for sleep – and intimacy,” says Dr Lee. He teaches Cognitive Behavioural Therapy for insomnia, a short, evidence-based behavioural approach that’s recommended by the NHS. A key tenet of the method is being strict about what you do and don’t do in the bedroom. Dr Lee says that ideally you won’t use it as a home office; that will constantly remind your brain of work when it should be resting. And it shouldn’t do double duty as a TV room or fitness studio. “Bad sleepers often use their bedroom as a place of recreation, where they might do knitting or sudoku, or read the newspaper,” says Dr Lee. The question he’s asked most often by patients is: ‘But can’t I even read in bed?’. “If you haven’t got a sleep problem, it may be fine to read in bed,” he says. “When you’ve tried not doing that for a month, and your sleep is better, then you can try reintroducing books.” Bedrooms need to look calm, too, for minimal brain stimulation, according to Nick Littlehales, sleep sports coach and author of Sleep: The Myth of 8 Hours, The Power Of Naps And The New Plan To Recharge Your Body And Mind. “You’re asking your brain to get some good mental and physical recovery, so you need to put it into an environment to help that process,” he says.

Think about what you’d be surrounded with if you were sleeping in nature, where humans would have originally slept. “The bedroom should bring the outside inside. If you’re thinking about colours, start with white. When it snows there’s no horizon, so there’s less for your mind to think about,” he says.

Research shows that light is the key signal that tells your body it’s time to be awake, and so ideally your bedroom should be in total darkness. If your curtains let in any light, it’s worth putting up a blackout blind. The room’s temperature is a hot sleep-science topic, too; sleep needs to be preceded by a tiny but essential dip in body temperature. “When we get tired in the evening, there’s a natural drop by half a degree Celsius. Getting chilly is a really good signal to get cosy in your nest," says Dr Lee. "Between about 18°C to 22°C is the sweet spot for most people. But some people will feel hot at 17°C." Adjust the bedding to suit what you like (see below).

When it comes to your bed, think big. King big, if you can, says Littlehales. He has a logical reason for this. Think back to your childhood, when you slept alone on a single mattress of 6ft x 3ft. “If you were to have another human being next to you, they need that amount of space, too,” he says. “And two single mattresses together make a king. It’s a real challenge for two adults to get a full night’s sleep in a regular full bed, especially when those adults are different sizes and have different bedding preferences,” he says.
 
We already know the temperature of the room is key, but it matters in bed, too. Research shows being too hot or too cold leads to less deep sleep.*
 
Littlehales advises washing bedding at least once a week, because newly put-on crisp bed linen feels not only cozy but cool and fresh against the skin, too. Temperature control also requires the right weight of comforter to suit the season and you; Scandinavian couples will often each have their own bedding. It’s worth considering a comforter each at the right tog for you and for the season, on top of two single mattresses zipped together, each with the right amount of give.
 

When it comes to mattress give, research shows lower back pain is one of the most frequent sleep disruptors, reducing both quality and quantity. However, there’s little expert agreement on which firmness of mattress might help prevent and reduce back pain; studies have shown conflicting results.**

The best overview so far comes from a 2019 review that looked at 39 studies.*** Over all these studies, the type of mattress that came out on top was medium firm. Ideally, says Littlehales, you should sleep lying on your side in a foetal position. And sleep on the opposite side to your dominant side (i.e. with your writing arm upwards), as this brings a feeling of safety. “Lying on the mattress, it should feel as if your body is releasing fully into its surface,” he says. It should also feel as if you don’t need a pillow to support your head. Indeed, you may find that with the right mattress, you may only need one, very shallow pillow.

When you fall asleep is defined by two interconnecting biological systems. The first is tiredness, the build-up of pressure to sleep while you’re awake. “From the moment we wake up, sleep pressure builds, and when we sleep it dissipates,” says Professor Foster. The second is your circadian system, which time stamps your life, telling your body it’s the right time in the 24-hour day-night cycle to sleep. Before you wake, it preps all your body systems to be ready for the biological day. For your most rejuvenating sleep, “the two systems should be aligned,” says Professor Foster.

But we disrupt this natural synchrony all the time, most severely by working a night shift or crossing time zones. Then sleep pressure will tell us to sleep, while circadian system says wake, or vice versa. But we also disrupt this balance in everyday ways; by staying up late or sleeping in, spending our lives inside, as well as by napping, eating and exercising at the wrong time (see below for the right times). Moving during the day creates the conditions for sleep later. “Sleep loves tiredness. Physical activity during the day will lead to physical inactivity at night. The same is true for mental activity,” says Dr Lee. In a study, people who did mind-body type exercise, such as tai chi and yoga, had better sleep than people who did aerobic exercise.****

But again, it’s light – or the lack of it – that’s the main signal for our bodies to be awake or to sleep. Professor Foster led the team that discovered specific cells in our eyes, photosensitive retinal ganglion cells (pRGCs), that register light and sync us into day and night. These cells are most sensitive to blue light; this makes sense because at dawn and dusk the light dominating the dome of the sky is enriched in blue light.

The issue in the modern world is that the light emitted by the screens of our devices is blue, too. This has led to a lot of warnings against evening screen use: specifically, that blue light prevents production of melatonin, the so-called sleep hormone, and so delays sleep. In fact, says Professor Foster, a lot of this advice is misguided. He points out that melatonin isn’t just a sleep hormone: “People who can’t make melatonin have fairly normal sleep,” he says. And that the light emitted by devices isn’t often bright enough to shift the body clock. In a classic study done at Harvard, people used Kindles on their brightest setting from 6pm to 10pm for five consecutive nights. This did alter melatonin levels – but it only impacted the time people went to sleep by nine minutes. “We need a lot of light for a relatively long duration to get an effect,” he says. What shifts your body clock is daylight, many thousands of times brighter than your screen or phone. On top of this, research now shows the more light you’ve been exposed to early in the day, the less that seeing light later on will shift your clock.” (See below for the best times to get daylight).
 

It does make sense to keep lights relatively low in the evening: inside light may not shift your clock very much, but it can make your brain more alert. And if you’re scrolling, to stick to neutral input. “There’s data emerging that increased alertness from social media seems to be the key issue, so I’d advise switching phones off 30 minutes before sleep,” says Professor Foster.

Sleep anxiety is real. The most common reasons people can’t get to sleep – or back to sleep – are anxiety and worry. You may be relieved to know that this can be explained biologically. Sleep has four stages: One is transitioning from awake to asleep, two is light sleep. Three is slow wave sleep, the deepest and most restorative stage. And the fourth stage is Rapid Eye Movement (REM) sleep, when you dream. To cycle through each stage takes roughly 90 minutes. This is mirrored when you’re awake, too: tiredness tends to wax and wane in 90-minute cycles.
 
When you’re in REM sleep, you can wake quite easily. Your limbic or emotional brain system is quite activated, as is your amygdala, the brain area associated with emotional memory. “We think dreams in REM are an emotional reprocessing and dissipating of the stresses and strains we have come across during the day,” says Dr Lee. That’s why you might wake in the middle of the night feeling panicked. “If this happens, wait. The cortex or thinking brain will switch back on and things won’t feel so desperate." Get out of bed and go and do something calm, like reading, for around 45 minutes. After that, you’ll be back at the tired stage of the 90-minute cycle and you’ll find you feel sleepy again. “If you stay in bed trying to get back to sleep, you might be so wound up by the time you get to your next dip, that you can’t get back to sleep,” he says.
 
People can also become anxious about not getting eight hours. “The myth of eight hours is a real problem. Because it’s not true!” says Dr Lee. “Ninety-five per cent of human adults sleep between six and nine hours. Some people only sleep for six and they feel fine… but they worry because they’re not getting eight. Some people need nine hours, but only get eight as they think nine would be lazy… but then they’re tired all the time.”
 

It’s more helpful if you think about sleep in terms of cycles, rather than hours, according to Littlehales. Over the course of the night you might ideally have five 90-minute sleep cycles, adding up to seven and a half hours. “But it’s the first two 90-minute cycles of sleep that are most important,” he says. ‘This is when your brain is trying to develop the deeper sleep rejuvenation stages of the 90-minute cycle.” If you wake in the early hours, it may even be that your brain has developed enough deep sleep in those first two cycles (or three hours).
 
Finally, watch out for a new form of insomnia, orthosomnia. “This is a sleep problem gifted to an otherwise good sleeper, from their sleep tracker freaking them out,” says Dr Lee. “Trackers aren’t accurate. It might say you’ve had 2% REM. But the only real way to detect this is by sticking electrodes on your head in a sleep laboratory.” By using a tracker, you’re copying a bad sleeper, because you’re focusing on sleep. “Good sleepers don’t think about sleep! Try to worry less – and don’t monitor something that doesn’t need monitoring!”
 

A regular routine does encourage good sleep; it helps coordinate your day-night rhythms with your levels of tiredness. The bad news is, it’s best to get up and go to bed around the same time seven days a week. Research shows that sleeping in at the weekend will help you catch up on some sleep – but not all.
 
Use the power of light in your routine, because it’s the biological signal that resets our inner clock, which then sets the time to sleep later, too. “Most of us should go outside and get as much morning natural light as possible,” says Professor Foster. This is because daylight is thousands of times brighter than electric light.
 
“Studies show that, for most people, morning light will advance the clock, and dusk light will delay the clock,” says Professor Foster. However, if you are a night owl who tends to go to bed and sleep in late, you will miss the morning light. “You’re then likely to be exposed to light in the later afternoon and early evening, which will shift your clock even later,” he says. If this is you and you do need to get up in the morning, it’ll be easier if you make it a daily habit to get morning light.
 
It’s fine to drink coffee, says Professor Foster. But bear in mind that enough caffeine to affect sleep stays in your system for around five to six hours. “Start the day with the strongest caffeine-rich drinks and then taper off after lunch, switching to decaffeinated by late afternoon,” he says.
 
When it comes to working out, the morning is optimal for sleep; you get extra points if it’s outside in daylight. Working out within an hour or two of bedtime may not be ideal, especially if it’s vigorous, as it’ll get in the way of the temperature drop you need to transition you from wake to sleep. The same is true of eating later, too.
 

If you wake in the early hours and then can’t get back to sleep, “try not to worry,” says Littlehales. “You can use the two natural recovery periods, midday (between 12pm and 2pm) or late afternoon (between 4pm and 5pm) to reset with a short, controlled recovery period (CRP), which past generations used to call a nap.” Professor Foster is less of a nap fan, saying that any nap needs to be less than six hours before bedtime. “If you’re napping that’s telling you you’re probably not getting enough sleep at night," says Professor Foster. There’s limited evidence for specific pre-bed relaxation routines, such as yoga or meditation. The key thing before end of day is to step back and do something to disconnect from the pressures of work and family. That might be light exercise, or mindfulness. “It’s really worth investing in whatever works for you,” says Professor Foster. The same is true for a bath, although research suggests you leave a little time to cool your temperature before bedtime. It makes sense to minimise light around two hours before bed. In particular, try not to brush your teeth in a very brightly lit bathroom. Then at least 30 minutes before bed, stop using devices. Finally, don’t ignore a yawn; it really is your own personal sign that you’re at the point in your 90-minute cycle when it’s best to call it a night and go to bed.

*ncbi.nlm.nih.gov/pmc/articles/PMC3427038/

**ncbi.nlm.nih.gov/pmc/articles/PMC8655046/

***Park SJ, Kim JS, JS CB. Comfort evaluation and bed adjustment according to sleeping positions. Human Fact Ergon Manufact Ser Ind. 2009;19(2):145e157

****__Sidharth et al 2014

Brigid Moss is a health writer, editor and co-author, with Professor David Nutt, of Psychedelics (Yellow Kite). Follow her on Instagram @brigidmoss