7 June 2021

Why you don’t need 8 hours of sleep at all, but at least 7 hours is recommended

 

By Ree Meertens and Merijn van de Laar

 

About a decade ago, sleep was the realm of sleep clinicians and psychologists. Sleep clinicians were concerning themselves with sleep-related diseases, like sleep apnea and narcolepsy. Psychologists were mostly interested in insomnia, and were developing effective non-pharmacological therapies for sleeplessness further.

At least 7 hours of sleep

This resulted in a need for clear recommendations to the general public about optimal sleep duration.  Independently, two US expert panels did extensive systematic reviews[1]. They discussed evidence of epidemiological studies, lab studies, and experimental field studies. One expert panel reached consensus about 7-9 hours sleep being recommended for people aged 18 to 65, and 7-8 hours for those over 65. Children and adolescents should sleep more, adolescents for example 8-10 hours.

The other expert panel recommended at least 7 hours of sleep for adults aged 18-60. An upper limit for sleep duration was not defined. Although long sleep duration (>9 hours) is related to mortality and disease, a substantial amount of experts thought this was probably due to residual confounding. This seemed likely as plausible biological pathways for long sleep being physiologically harmful were lacking.

Both expert panels could not reach consensus about whether a sleep duration of 6 hours is adequate. In the panel that evaluated the evidence for ages 18 to 65, there was disagreement about whether 6 hours of sleep is appropriate for some disease categories (e.g. cardiovascular health, 6 hours was appropriate according to part of the experts), but not for others (e.g. metabolic disease, for which 6 hours consensually was judged not appropriate).  Part of the experts of the other expert panel judged that 6 hours of sleep was adequate in general, and it was stated that 6-10 hours of sleep might be appropriate for some people 18-60.

Written by:

Dr. Ree Meertens is associate professor Health Promotion (RL Promoting Health and Personalised Care)

Dr. Merijn van de Laar is Deputy Head of the General Practitioner Training Programme and sleep researcher. He recently wrote the book "Slapen als een oermens".

Focus on sleep quality

So to be safe, ‘at least seven hours of shut-eye’ seems the recommendation. However, there is another side to the story. For a lot of people who sleep less than 7 hours, it is not their own choice. They try to have a good night’s sleep, but they simply don’t succeed. It is estimated that about 20% of the Dutch population experiences trouble sleeping.  For them, the recommendation that they should sleep more than 7 hours may just result in lying awake longer, more stress, more sleeplessness, and even mental complaints.

Furthermore, sleep duration and sleep quality are strongly related. People who report short sleep are often also bad sleepers, and worse sleep quality is also associated with worse health outcomes. A good advice on sleep duration therefore has to incorporate sleep quality as well.

The recommendation ‘seven hours or more’, may also lead to confusion while the NHG preferred treatment for insomnia (Cognitive Behavioral Therapy for Insomnia) first focuses on sleep quality, and not on sleep quantity. So, therapists who treat insomniacs, first try to optimize sleep quality by restricting bed times, they stress that one can function well on little sleep (e.g. 4.5 to 5 hours of good quality sleep).

How confusing..

A picture of somebody not able to sleep.

This of course complicates communication to the general public. Expert A says that 7 hours or more is recommended, while expert B says that 5 hours is appropriate. And then there is expert C, saying that you cannot give any advice to the general public at all, as sleep is so individual.

This kind of complication is relatively new to the healthy lifestyle field, due to sleep being only partly under voluntary control. Also, sleep is extremely multifaceted, encompassing sleep quality, sleep quantity and sleep timing as important factors to be taken into account. Furthermore, the complication may be related to sleep being ‘the new kid on the block’ in public health. Not all sleep experts are used to giving this kind of lifestyle advice to the general population. It is never really sure that a certain lifestyle recommendation (e.g. ‘eat two pieces of fruit daily’) holds for an individual. He might insist that he does well on one fruit a week, and he may be right. But nevertheless the best advice for us to give (and for him to follow) is ‘two fruits a day’.

Sleep is very important. For (almost) everything

So, a good sleep recommendation will take a few lines, instead of one. The recommendation needs to take into account sleep quality and sleep timing, as well as sleep duration.

Let’s work on that.

To be sure, there is one issue where sleep experts of the various flocks don’t have different point of views about: Sleep is very important. For (almost) everything.

[1] Watson, NF et al., 2015, http://dx.doi.org/10.5665/sleep.4886, Hirshkowitz, M et al. (2015), http://dx.doi.org/10.1016/j.sleh.2015.10.004, see also Chaput J-P et al. (2020) https://doi.org/10.1139/apnm-2020-0034