Updated: Sep 18, 2022
Everything we do, we do better after a good night’s sleep. But are we getting enough sleep and what steps can we take to improve our sleep quality?
Why sleep matters
Sleep is vital to our health and lack of sleep can lead to health problems or make existing conditions worse. In the UK, 51% of adults report sleeping less than 6 hours per night and 50% describe their sleep as poor quality . Consistent lack of sleep significantly increases the risk of diabetes, high blood pressure and obesity, and predisposes to poor mental health .
In addition, sleep is essential to maintaining concentration, productivity and safety whilst driving. Sleep deprived drivers have similar mental impairment to drunk drivers; 24 hours without sleep has a greater impact on driving performance than a blood alcohol concentration of 50mg/100ml (Scottish drink-drive limit)  and many people are killed or seriously injured each year after falling asleep at the wheel .
 Infographic from Sleep Foundation (published March 2022)
How much sleep do we need?
Most adults need between 7 – 9 hours of sleep per night to maintain health and optimal mental function. Older adults need the same amount but may experience an initial 3–4 hour period of deeper sleep, followed by a period of lighter sleep. Teenagers and children need even more sleep, sometimes as much as 12 hours or more to perform at their best .
A single night of reduced sleep will make you feel tired the next day, but it won’t harm your health. However, after several nights of poor sleep, you are likely to feel a consistent lack of energy, slowed thinking, irritability and difficulty concentrating. Repeatedly missing out on sleep can also leave you vulnerable to depression and anxiety, as well as the physical health issues previously mentioned .
Sleep quality matters too
The quality of our sleep is almost as important as the number of hours we spend in bed. For example, a person who sleeps for eight hours but wakes many times in the night may still have insufficient sleep, despite the duration of sleep being adequate. We can improve our sleep quality by ensuring our bedroom environment is optimised (not too hot, cold or noisy) and by establishing a routine around bedtime, making sure we spend time winding down before actually going to bed.
Winding down involves reducing the amount of mental and physical activity we do in the hours immediately before going to bed. Too much mental activity means that our minds continue to race after going to bed, and too much physical activity will result in elevated adrenaline levels which can also keep us awake. Reducing screen time and ambient light levels prior to sleep is also important, as this allows maximum melatonin production in the brain, a natural chemical (neurotransmitter) that aids sleep. We suggest shutting off all screens and doing something relaxing, like reading a book, listening to music or taking a bath, at least one hour before your planned bedtime.
How sleep works -
Sleep stages, cycles, REM & non-REM sleep
During a full night’s sleep, our bodies cycle through five stages of sleep, multiple times. There are four stages of ‘non-REM’ sleep, followed by one stage of ‘REM sleep’. REM stands for Rapid Eye Movement. During REM sleep our eyes move rapidly under our eyelids, but don’t send any visual information to the brain, whereas this doesn’t happen during non-REM sleep. Each cycle through all five stages of sleep takes between 90 – 120 minutes to complete. With each subsequent cycle, we spend increasing periods of time in REM sleep, with most REM sleep occurring in the latter half of the night  . The infographic below outlines the sleep cycles during a typical 8-hour night’s sleep.
 Infographic from Why We Sleep by Matthew Walker (published Feb 2019)
REM & non-REM sleep for good health
Both REM and non-REM sleep are important for health because each serves a different physiological function. When we first fall asleep, non-REM sleep begins, comprising stage 1 (awake/light sleep), stage 2 (light sleep) and stage 3/4 (deep sleep). The deep sleep stages of non-REM sleep are especially important because our bodies repair and regrow damaged tissues and strengthen the immune system during this phase. As we age, we naturally tend to sleep more lightly and spend less time in deep sleep, although research shows that we still need a similar amount of sleep as when we are younger .
REM sleep (stage 5) follows non-REM sleep, usually starting around 90 minutes after falling asleep, with each subsequent cycle of REM sleep becoming longer (see infographic). REM sleep is commonly associated with dreaming (although dreaming can also occur in non-REM sleep), but it is also vital for memory consolidation, emotional processing, brain development and wakefulness preparation .
Because most REM sleep occurs later in a full night’s sleep, people who don’t get sufficient hours or quality of sleep, can struggle to get enough REM sleep and are therefore deprived of its many benefits. There are also several sleep disorders associated with abnormal REM sleep, including narcolepsy, sleep apnoea and nightmare disorder (see below for more on sleep disorders).
To read more about the different stages of sleep and their functions, please see the Sleep Foundation’s useful guide here.
How to improve your sleep
Poor sleep has multiple causes but is most often linked to lifestyle and our behaviours around bedtime, collectively known as ‘sleep hygiene’. Research consistently points to several concrete steps that promote better sleep, and whilst doing all these steps might seem overwhelming, implementing even one of them will likely improve your sleep. Working towards better ‘sleep hygiene’ can greatly improve the likelihood of consistent, restful sleep.