Sleep is generally accepted as a focal part of the recovery process for athletes and believed to be important to performance. Many athletes track their sleep and aim to get the recommended 7-9 hours of sleep per night (1). How much we actually need, is not known, and may be highly individual. There is another reason why sleep may be important: anecdotally athletes who don’t sleep well, seem to get ill more often. However, few studies have investigated the effects of sleep quality on immune function. Therefore, Professor Neil Walsh and his team at Liverpool John Moores University in the UK decided to investigate the relationship between sleep and immune health a bit further (2). If you want to know what they found continue reading!
Athletes don’t always sleep well
We know that despite the widespread belief that sleep is important for athletes, there are many athletes who don’t get the hours and sleep and the quality of sleep they believe they need (Read this blog). In the study discussed in that blog, athletes were spending more time in bed when training intensified but they did not sleep more. There was also an increase in the number of wake bouts throughout the night and a more fragmented sleep overall.
Why do athletes have poor sleep?
There are many reasons why athletes may not sleep the hours they require. Sometimes this has to do with training times (for example swim training often has very early starts and several team sports typically have very late training times which can make it harder to fall asleep). It is also possible that athletes are juggling too many things, in addition to their training, and usually the variable that needs to give, is sleep. During periods of hard training or when athletes are increasing their training load, the extra stress may also have an impact on sleep. Research shows that adults who habitually fall short of the recommended 7–9 hours sleep each night are more susceptible to respiratory infections (3, 4).
Study on effects of sleep on immune health
The study by Prof Walsh and his team was performed in more than 1300 army recruits who were engaged in a 12 week training program (about two thirds were men and one third women). The researchers had recruits report on their sleep before they joined the training. They then divided the group in two: One group consisted of individuals who slept their habitual hours during the 12 week training and another group who slept 2 hours (or more) a night less than their habitual sleep. Sleep duration was recorded and perception of the quality of sleep was monitored. They then recorded physician-diagnosed upper respiratory tract infections (URTI).
What did the study find?
The first finding of the study was that sleep restriction had an effect on URTI. Sleep restriction resulted in a 3 time higher risk of infections! This confirmed some earlier reports. However, the new and far more interesting finding was that this relationship was largely driven by the perceived quality of sleep. Those recruits whose sleep was restricted AND reported poor quality of sleep had a more than 2 time greater chance of getting an URTI. On the other hand, the group that was sleep restricted but reported good sleep quality, seemed to be protected and were at no greater risk of URTI compared with the reference group.
These findings are interesting because athletes (and most non-athletes as well) place so much value on the hours they sleep. However, this study shows that the quality is equally important. So what can athletes do to improve their sleep quality? Watch the video below by Prof Neil Walsh to find out:
Summary
The new study found that:
sleep restriction was associated with increased URTI susceptibility during training and
most notably, the observed association between sleep restriction and URTI was driven by recruits reporting poor sleep quality.
In practical terms this means that athletes should focus on improving sleep quality and not just hours of sleep. Some guidelines are provided here and in several previous blogs:
References
Walsh NP, Halson SL, Sargent C, et al Sleep and the athlete: narrative review and 2021 expert consensus recommendations British Journal of Sports Medicine 2021;55:356-368. http://dx.doi.org/10.1136/bjsports-2020-102025
Walsh et al Sleep 2022. LINK: https://academic.oup.com/sleep/advance-article/doi/10.1093/sleep/zsac222/6702165
Prather AA, Janicki-Deverts D, Hall MH, Cohen S. Behaviorally assessed sleep and susceptibility to the common cold. Sleep. 2015;38(9):1353-1359.
Cohen S, Doyle WJ, Alper CM, Janicki-Deverts D, Turner RB. Sleep habits and susceptibility to the common cold. Arch Intern Med. 2009;169(1):62-67.
