356 Walsh NP, et al. Br J Sports Med 2021;55:356–368. doi:10.1136/bjsports-2020-102025 Sleep and the athlete: narrative review and 2021 expert consensus recommendations Neil P Walsh , 1 Shona L Halson, 2 Charli Sargent, 3 Gregory D Roach, 3 Mathieu Nédélec, 4 Luke Gupta, 5 Jonathan Leeder, 6 Hugh H Fullagar, 7 Aaron J Coutts, 7 Ben J Edwards, 1 Samuel A Pullinger , 1,8 Colin M Robertson, 9 Jatin G Burniston, 1 Michele Lastella, 3 Yann Le Meur, 4 Christophe Hausswirth, 10 Amy M Bender, 11 Michael A Grandner, 12 Charles H Samuels 13 Consensus statement To cite: Walsh NP, Halson SL, Sargent C, et al. Br J Sports Med 2021;55:356–368. For numbered affliations see end of article. Correspondence to Professor Neil P Walsh, School of Sport and Exercise Science, Liverpool John Moores University, Liverpool, UK; n.walsh@ljmu.ac.uk Accepted 30 September 2020 Published Online First 3 November 2020 © Author(s) (or their employer(s)) 2021. No commercial re-use. See rights and permissions. Published by BMJ. ABSTRACT Elite athletes are particularly susceptible to sleep inadequacies, characterised by habitual short sleep (<7 hours/night) and poor sleep quality (eg, sleep fragmentation). Athletic performance is reduced by a night or more without sleep, but the infuence on performance of partial sleep restriction over 1–3 nights, a more real-world scenario, remains unclear. Studies investigating sleep in athletes often suffer from inadequate experimental control, a lack of females and questions concerning the validity of the chosen sleep assessment tools. Research only scratches the surface on how sleep infuences athlete health. Studies in the wider population show that habitually sleeping <7 hours/ night increases susceptibility to respiratory infection. Fortunately, much is known about the salient risk factors for sleep inadequacy in athletes, enabling targeted interventions. For example, athlete sleep is infuenced by sport-specifc factors (relating to training, travel and competition) and non-sport factors (eg, female gender, stress and anxiety). This expert consensus culminates with a sleep toolbox for practitioners (eg, covering sleep education and screening) to mitigate these risk factors and optimise athlete sleep. A one-size-fts-all approach to athlete sleep recommendations (eg, 7–9 hours/ night) is unlikely ideal for health and performance. We recommend an individualised approach that should consider the athlete’s perceived sleep needs. Research is needed into the benefts of napping and sleep extension (eg, banking sleep). PREAMBLE An ever-growing volume of peer-reviewed publi- cations speaks to the recent and rapid growth in scope and understanding of sleep for optimal athlete health and performance. More than 80% of all peer-reviewed publications on this topic have been published in the last 10 years (>1 000 papers using the search terms ‘sleep’ and ‘athlete’, Web of Science). Herein, a panel of international experts review the current knowledge on sleep and the athlete, briefly covering the background, exploring continued controversies, highlighting fruitful avenues for future research and providing practical recommendations. The introduction section covers the need for sleep, including sleep architecture and the restor- ative benefits of sleep for the brain and body. Pitfalls and challenges measuring athlete sleep are reviewed, and practical recommendations provided. The following section, entitled sleep and the athlete, covers the influence of sleep inadequacy and sleep extension on athletic performance. We review the evidence that elite athletes are particularly suscep- tible to sleep inadequacy, for example, during inten- sified training and in those reporting symptoms of over-reaching and overtraining. The final section, entitled strategies to improve sleep, provides prac- tical recommendations to alleviate the symptoms of jet lag, nutritional strategies to enhance sleep and a toolbox for practitioners to manage and optimise athlete sleep. INTRODUCTION The need for sleep Normal human sleep comprises two main types— non-rapid eye movement sleep (non-REM) and REM sleep. 1 Non-REM sleep is divided into three stages, representing a continuum from ‘light’ sleep in stages 1 and 2, through to ‘deep’ sleep in stage 3. 2 The duration and composition of normal sleep changes across the life cycle. At the ages most rele- vant to aspiring and established athletes, a sleep of 8–10 hours for an adolescent (aged 15 years) contains approximately 57% light sleep, 22% deep sleep and 21% REM sleep; and a sleep of 7–9 hours for a young adult (aged 30 years) contains approx- imately 61% light sleep, 16% deep sleep and 23% REM sleep. 3 Sleep is essential for the brain and the body. Proto- cols with one or two nights of total sleep depriva- tion or 1 or 2 weeks of partial sleep restriction have been used to demonstrate the importance of sleep for both mental and physical health. In particular, sleep loss impairs cognition, 4 learning and memory consolidation 5 and mental well-being 6 ; it disrupts growth and repair of cells, 7 metabolism of glucose 8 and lowers the protective immune response to vaccination 9 10 and resistance to respiratory infec- tion (see online supplemental file 1 for more exten- sive review on the need for sleep). 11 Measuring sleep With the increasing popularity of measuring sleep within both medical and consumer fields, unsur- prisingly, the number of sleep measurement tools is rapidly increasing (table 1). Some of the more common measurements regarding sleep include: sleep architecture (sleep staging), sleep duration, on December 9, 2021 by guest. Protected by copyright. http://bjsm.bmj.com/ Br J Sports Med: first published as 10.1136/bjsports-2020-102025 on 3 November 2020. Downloaded from