NHS guidance says that adults should aim for between 7 and 9 hours’ sleep a night. Should we worry if we’re not achieving that? And what does it mean for our health if we don’t get enough sleep?
Simon Kyle is Professor of Experimental and Clinical Sleep Research at the University of Oxford and NIHR Oxford Health Biomedical Research 
Centre. He explains how research is helping us understand the complex relationship between sleep and health.
First, the obvious question: should everyone be having around eight hours’ sleep a night?
On average, adults should be aiming for somewhere between 7 and 9 hours. The reality is that it’s very individual and people need to work out what their own sleep ‘need’ is. For some people, six hours might be appropriate, whereas others might need nine. But how long you sleep for is just one of many factors that affect sleep health.
Research shows that when you sleep is also important: how your sleep coincides with light and darkness and whether you sleep at regular times. The timing and regularity of sleep is particularly relevant to our biological (or circadian) clock. Continuity is another factor: whether your sleep is in a solid block or broken up.
How you view your sleep also matters. If you wake feeling refreshed and that you’ve had a good night, then you’ve probably had enough sleep for your own needs.
Another test is whether you have bouts of sleepiness or involuntary naps during the day. If so, that’s a sign that you’re not getting enough quality sleep, or that another sleep disorder may be disturbing your sleep. You need to work on all these factors to get the benefits of sleeping well.
What impact does poor sleep have on our health?
Poor sleep is linked to an increased risk of anxiety, depression and dementia. It can also increase your risk of high blood pressure and stroke. Disrupted sleep is also connected to metabolic disorders like diabetes and obesity. One recent study showed it can increase your risk of having more than one chronic condition.
We get this broad picture of sleep patterns and health by analysing data from large cross sections of the population. For example, we recently introduced a sleep questionnaire into the UK Biobank, and found that a quarter of respondents met criteria for a possible sleep disorder. This important information, when combined with other data, should now enable us to better understand, for example, the genetic underpinnings of different sleep disorders and how sleep issues link to other health issues. But this type of research can’t tell us if treating sleep disorders leads to improvements in these health conditions.
To do this, you need research that trials treatments in people with sleep difficulties. We’ve just completed the RESTED trial, to see whether improving sleep patterns through a behavioural therapy can also treat depression. We’re currently analysing the results.
Are there treatments that can help you sleep better?
Absolutely. Most people know of sleeping pills, which are recommended for short-term use. They can help some people, but they aren’t the first-line recommended treatment for insomnia. Cognitive behavioural therapy (CBT) is the most effective treatment to improve sleep quality in people with long-term insomnia.
However, very few people can access CBT for insomnia, because it is typically delivered by a clinical psychologist over 6-8 weeks. We trialled a shorter version of one element of the recommended CBT programme – called sleep restriction therapy. We trained nurses to deliver this therapy through GP practices in just 4 brief sessions, as a more cost-effective and accessible treatment option. We found that it was effective in improving insomnia, and benefits lasted for the following 12 months. We also found it improved mental health, productivity at work and reduced work absences.
What’s next for sleep research?
It’s quite exciting, because we don’t fully know what difference we could make to a whole range of health outcomes by improving sleep patterns. There are more trials now looking at the wider impact of treatments for sleep disorders. And we also want to understand why improving sleep can lead to other health benefits and how this process works.
Another new research area is looking at the impact of light and the timing of food intake for our sleep and circadian health. Humans are not naturally nocturnal animals, so we’ve evolved to be active and to feed during daylight hours and to sleep at night. But in the modern world, our lives are very different. We spend 90% of our time indoors. We get less natural light and are often exposed to artificial light at night. This is even more pronounced for shift workers.
There’s evidence that you can influence the timing, quality and continuity of sleep by changing the kind of light you’re exposed to during the day. Other evidence suggests that better alignment between our circadian rhythms and the timing of meals may have benefits for metabolic health. An important theme of the sleep research in the NIHR Oxford Health Biomedical Research Centre is to ask how we can translate what we know about these natural rhythms into therapies that we can then test in patients to see if we can influence disease. We’re also looking at how to help shift workers cope better with the disruption that their work causes to natural sleep patterns.
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