Discussion
The prevalence of sleep disorders among professional soccer players was 68.5%. Further, a concerning level of poor sleep quality (PSQI), daytime sleepiness (ESS) and moderately severe clinical insomnia (ISI) was seen in players (see table 2 and figure 1) alongside self-reported insufficient sleep durations compared with established NSF guidelines (8–10 hours).10 The high sleep efficiency observed in this population (96.4% of the sample had sleep efficiency >85) is indicative of insufficient sleep durations, given short sleepers may have high sleep efficiency. However, short sleepers may also have very poor sleep efficiency when quantity and quality are both impaired, for example, in the case of insomnia.
Late bedtimes (bedtime ~00:24) and sleep interruptions (~13%) likely contributed to the self-reported poor sleep quality of players in this study. Insufficient sleep duration and quality has negative effects on athletic performance,1 injury susceptibility,2–4 illness risk,5 wound healing,6 academic performance,7 8 holistic well-being and athlete development.9 Indeed, the late bedtimes observed in this population suggest an evening chronotype and/or delayed sleep phase syndrome, which are implicated in sleep debt and chronic underperformance.29 While the present study did not directly access the relationship between sleep and the afore-described athletic performance relevant effects, the self-reported sleep characteristics are not facilitative of optimal athletic performance and recovery, and long-term athlete development. Therefore, the self-reported sleep results will be of concern to practitioners in the Middle East. Indeed, average sleep quality in the present study (PSQI: 5.6±2.1) was poor compared with elite Australian football (Australian Football League) players (PSQI 4.3±1.6)30 and elite European soccer players (PSQI 3.6±2.4),31 but comparable (5.6±2.3) across a mixed sample of highly trained team sport athletes (predominately Rugby 7’s/15’s and cricket).24 The prevalence of clinical sleep disturbance (PSQI ≥5) in this study was 68.5%, this was higher compared with Brazilian multisports elite athletes (38%)32 and team sports athletes (50%).24
Cultural and environmental factors likely dictate late bedtimes and early rising in QSL players, resulting in suboptimal sleep durations, as detailed elsewhere.9 12 14 Specifically, early morning and/or late evening training/competition within high environmental temperatures33 alongside late evening nutritional needs and early morning prayer are not conducive to the recommended earlier sleep onset times to offset early rising, in order to gain sufficient NSF endorsed (7–9 hours) sleep durations.14 These factors combine to provoke late evening active meal digestion,34 various inflammatory biological cascades35 and increased arousal and body temperatures,36 37 when players are attempting to sleep. These can all negatively influence favourable sleep characteristics34–37 and appropriate nutritional intake,38 39 thus holistic player recovery is likely impeded.40 41 Alongside these challenges the player still has to engage in their everyday activities and commitments, potentially limiting further their time available for sleep. It appears, at least superficially, that changing training/competition scheduling would be an easy solution with regard to enhancing time available for player sleep; however, as outlined here and elsewhere9 14 it is simply not feasible given the holistic local environment. Appropriate daytime nap scheduling may have some utility within the presented paradigm to increase sleep durations and favourably influence performance recovery.42–46
Uninterrupted sleep, particularly in the initial stages of sleep, enhances sleep quality47 and other holistic quality of life measures.48 Leading player explanations for the sleep disturbances surfaced in the present data were a visit to bathroom (27.9%) and ‘feeling too cold’ (13.5%). Players likely consume large volumes of fluid/food in a relatively short space of time after evening training/competition alongside persistently high body core temperatures. There is natural decrease in the core body temperature during sleep initiation49 and this may potentially explain sleep disturbances, that is, ‘feeling too cold’ in addition to the common practice in the region whereof air-conditioning being set too low for a full night’s comfortable sleep when evening temperatures are high. It is therefore not surprising that the need to visit the bathroom and feeling too cold are reported as predominant factors for sleep disturbances within the present population. Appropriate aggressive postcompetition/training cooling manoeuvres50–52 alongside optimally prescribed fluid intake volume and composition (to reduce urine losses)53 may reduce the frequency of these disturbances. A recent study among youth soccer players demonstrated that hot showers prior to bedtime can improve sleep latency by 7 min and sleep efficiency by 2%.54 Sleep disturbances in the present study (13.5%, table 2) are lower compared with elite team sports players from Australasia (34.6%),24 however the present experimental design does not provide insight into the mechanism(s) behind these differences aside from the demographic of players.24
The median body fat % of the athletes included in this study was 19.8% with IQR of (17.3%–24.1%), this could be viewed as relatively high, although body fat % was not associated with any PSQI, ISI or ESS-derived outcomes. The association of BMI and sleep disorders is described as U-shaped relationship with lower BMI and obesity presenting a higher risk for the presence of a sleep disorder.55 The present data found that the average BMI of players with ESS >8 was lower compared with players with normal ESS scores (table 3). Approximately 10% of players reported sleep medication use, similar to the 2014 National Collegiate Athletic Association report where 10% of miscellaneous substance use was represented by sleep medication.56
The presented data and discussion thereof must be tempered by the experimental limitations presented. Indeed, sleep was not assessed quantitatively and a non-athletic control group was not employed, future designs would benefit from such inclusions. However, in practice, the ability to quantitatively assess a large sample of players sleep via actigraphy and/or PSG has practical and logistical limitations.9 Therefore, the easily administrable qualitative questionnaire approach may offer a practically compatible first-step (triage) towards identifying sleep issues within large squads of players allowing economical prescription of quantitative assessment of valid player subsets. A recent systematic review and meta-analysis of studies that monitored sleep among team sports athletes supports this notion, they concluded that sleep efficiency using actigraphy or PSQI are both indicative of sleep quality.57 Future research could benefit from employing the methods adopted here, at different stages of the season (which could include Ramadan), to provide greater understanding of the magnitude of challenge these athletes face to obtain appropriate sleep across a season. Unfortunately, data related to injury and illness were not accessible for the population used within the present design, other similar designs would benefit from the inclusion of such measures. In addition, there was a general response/recall bias because the sleep characteristics reported were based on the recall of sleep behaviour within the preceding month. While the PSQI is a valid instrument to measure sleep characteristics, it does not capture the duration of daytime naps. It is quite possible that athletes in our study compensate for the lack of adequate night-time sleep with naps. Interpretation of the presented data should be conducted carefully relative to these experimental limitations.
Practical applications
The employed questionnaires in this study quickly (15–20 min per player) revealed worrying sleep characteristics in many players and thus practitioners may consider the employed questionnaire battery as a simple time-efficient approach to identify (triage) a subset of players from a large squad, who may benefit from further sleep-specific medical support and/or quantitative sleep assessment. The data reinforce the need for player and staff education regarding the importance of sleep relative to various aspects of athlete development, training, competition, recovery and health, and the need for regular sleep focused screening, monitoring and assessment within athletes; particularly within team sports athletes. Miles et al20 identified barriers to such an approach (mainly lack of resources, busy schedule and lack of knowledge of sleep hygiene) to promote/incorporate healthy sleep behaviour among soccer teams. Providing player and practitioner focused palatable educational resources may facilitate building a culture of healthy sleep behaviours and hygiene within a soccer team environment.
