LETTER TO THE EDITOR Comment on: ‘‘Does Elite Sport Degrade Sleep Quality? A Systematic Review’’ Amy M. Bender 1,2 • Charles H. Samuels 1,2 Ó Springer International Publishing Switzerland 2017 The review article by Gupta et al. in a recent issue of Sports Medicine has provided the sleep and sport science com- munity with a methodologically sound systematic review of the literature on sleep in elite athletes [1]. The review included research studies with multiple methods for assessing sleep including objective measures of polysomnography (PSG) and actigraphy, as well as sub- jective measures using questionnaires. The authors acknowledge the quality of evidence was low with poorly designed research studies and few studies with compar- isons to non-athlete controls. Based on the evidence available, the authors conclude that ‘‘elite athletes gener- ally show a high overall prevalence of insomnia symptoms characterized by longer sleep latencies, greater sleep fragmentation, non-restorative sleep, and excessive day- time fatigue.’’ The focus of the review was on insomnia symptoma- tology with pre-sleep cognitive hyperarousal as a main cause. However, we should also consider another potential cause rarely assessed in the sleep and sport literature thus far. Circadian misalignment is not only present after transmeridian travel, but could also potentially be present in athletes who have delayed or advanced sleep phase syndrome. Athletes who are morning types would not likely suffer from insomnia, but those who are evening types may have difficulties falling asleep within the ideal 30-min window. The standard advice to ‘‘go to bed at a reasonable hour’’ may not align with the athlete’s endogenous sleep phase and could exacerbate insomnia symptoms in those athletes. Future research and sleep screening tools must assess chronotype to identify athletes who are misaligned with the imposed training or compe- tition schedule. It is also important to understand that insomnia is only one of many clinically relevant sleep and circadian disor- ders that contribute to poor sleep quality in elite athletes. One of the studies cited in the review found that 50% of 175 elite rugby and cricket athletes [2] were identified as being poor sleepers according to the Pittsburgh Sleep Quality Index (PSQI) [3]. If we assumed this was only due to insomnia, we would miss the fact that 38% of the sample identified themselves as being snorers and 8% were reported to have apneic episodes, both indicative of obstructive sleep apnea. In addition, 28% of the sample also had clinically significant levels of excessive daytime sleepiness, a symptom not present in those suffering from insomnia. While the prevalence of clinically significant sleep and circadian disorders is low, the diagnosis and management of these disorders is critical to the perfor- mance and well-being of the athlete and the team. Although the sleep duration of elite athletes was similar to non-athlete controls [1], we cannot discount it as a potential contributor to poor sleep in elite athletes. Recommendations for a normal adult are between 7 and 9 h of sleep per day [4], with athletes needing more. The average sleep duration across the 23 studies in Table 2 [1] is only 7.3 h of sleep. It is likely that this lack of sufficient sleep is also contributing to the high prevalence of sleep complaints in athletes. Another important point to consider is that the most widely used questionnaire by studies in this review was the & Amy M. Bender abender@centreforsleep.com 1 Centre for Sleep and Human Performance, 106, 51 Sunpark Drive SE, Calgary, AB T2X 3V4, Canada 2 Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada 123 Sports Med DOI 10.1007/s40279-017-0712-4