Professor Russell Foster shares why the “eight-hour rule” is not as universal as many believe.

Do you really need eight hours of sleep every night? And how much can everyday factors like noise, light and stress affect the quality of your rest?

Sleep is often talked about in simple rules, but the science behind it is far more personal and complex. To better understand what truly supports good sleep, we spoke with Professor Russell Foster, Head of Oxford’s Nuffield Laboratory of Ophthalmology, founder and Director of the Sleep and Circadian Research Institute, and Fellow of Brasenose College, Oxford.

Professor Foster’s research explores how circadian rhythms and sleep are generated and regulated, as well as what happens when these systems are disrupted by societal pressures, age and disease. In this Q&A, he shares why the “eight-hour rule” is not as universal as many believe, how environmental factors such as noise and artificial light can interfere with sleep, and why managing stress may be one of the most important steps toward better rest.

1. What is the biggest misconception people have about sleep today?

That you have to get eight hours! There is huge individual variation in sleep need, and for adults, the National Sleep Foundation suggest the healthy range is between six and eleven hours. Yes – the average across the population is around eight hours but this should not be used as a standard. Sleep is like shoe size “one size does not fit all”. So how do you know you are getting the sleep you need? It’s simple. You are not getting enough sleep if you: (i) feel that you do not perform at your peak during the day; (ii) “over-sleep” extensively on free-days (weekends and holidays); (iii) are dependent upon an alarm clock/another person, for you waking you-up; (vi) take a long time to wake up and have “sleep inertia”; (v) feel sleepy, irritable & fatigued when awake; (vi) crave a nap during the day; (vii) crave caffeinated and sugar-rich drinks; (viii) are  irritable, show a loss of empathy, do not consider the consequences of actions.

2. How much do environmental factors, such as noise, affect sleep quality?

Light and noise can have a big impact on your ability to sleep, preventing you from getting to sleep and then staying asleep. This is a particular problem for individuals in lower socio-economic groups living in crowded cities, where there is excessive traffic noise, street lighting and/or noise from airports or train stations. Recent data suggests that “artificial light at night” (ALAN) can act to increase alertness and disrupt sleep. Such poor sleep has been liked to a greater risk of stroke, heart attacks, type 2 diabetes, obesity, cancer and poor mental health. A recent House of Lords Report described light and noise as the “neglected pollutants” for our sleep health:

https://publications.parliament.uk/pa/ld5803/ldselect/ldsctech/232/23202.htm

3. If you could give one piece of advice to someone who wants to improve their sleep, what would it be?

Most people do not have a sleep problem, rather their sleep is affected by anxiety and stress. Stress is the key enemy of sleep. As a result, it is critical to “de-stress” as much as possible several hours before you go to bed. Step back from the pressures of work and family and find ways of relaxing that work for you. This may be yoga, mindfulness, a relaxing bath, listening to calming music or reading a few pages of your favourite novel. Don’t discuss stressful topics while lying in bed with your partner - that can wait! Don’t “doom scroll” on your Smartphone; make your bedroom a place of calm and tranquillity; invest in good pillows, mattress and duvet; remove devices such as TVs and computers; use black-out blinds if street lighting is a problem. If you wake in the night stay calm - its normal to wake up for short periods. If you don’t get stressed you will almost certainly fall back to sleep.

For more information read Life Time: The New Science of the Body Clock, and How It Can Revolutionize Your Sleep and Health by Russell Foster and published by Penguin Books.

For his work, Russell was elected to the Fellowship of the Royal Society in 2008, the Royal Society of Biology in 2011 and the Academy of Medical Sciences in 2013.  Russell was honoured by being appointed as a Commander of the British Empire (CBE) in 2015 for services to science. Russell has published over 300 scientific papers and has received multiple national and international awards. He has written five popular science books. His fifth for Penguin (Yale University Press in the USA), entitled Life Time was published in March 2023 and became a bestseller in both hardback and paperback. His new book entitled How Light Gives Us Life will be published in March 2027.