Sleepiness among Professional, Semi Professional and Students Chinese Soccer Players in the Shanghai Lockdown

1. Introduction

After decades of focusing merely on the performance, there is more public awareness on the wellbeing and quality of life of the athletes and consequently research in the field has increased [1]. Well-being in sport performance has been thus investigated, to increase the health of the athlete/worker. Among the parameters who affect the quality of life, sleep has a significant role. Sleep is a determinant of many illnesses and relates to several psychological and physical diseases [2], not to mention the effect of sleep on performance. In athletes, poor sleep quality has been reported more by female athletes than by male athletes: 31.4% of men and 48.8% of women had poor subjective sleep quality [3] and females experience diminished total sleep times [4,5]. Also, elite athletes seems to have shorter sleep than lower-level athletes [4,5]. Some explanation has been proposed for sleep shortage in professional athletes. Physiological causes has been advocated, such as hormonal activation (adrenal axis arousal) and induced by physical activity [6]. Forced exercise has been shown to cause circadian phase shifts in the kidney, liver, and submandibular glands by activating the sympathetic nervous system and the hypothalamus-pituitary-adrenal gland axis [7]. Beside these factors, it has been hypothesized that Elite athletes can possess personality characteristics which predispose to success in elite sport (i.e., perfectionism and anxious concern) which also predispose individuals to sleep disturbances [8].

The Covid-19 Lockdown also impacted athletes training [9,10] and powerful impacted lifestyles. Beside the worsening of the performance and the increased rate of injury, psychological and mood states were altered in male and female professional and non-professional soccer players, by the restriction imposed by Covid 19 epidemic, increasing depression and anxiety [9]. Sleep quality and length has also been affected significantly by the lockdown. In a study performed on 175 Spanish football players of different level, males and females reported a worse sleep than before lockdown, and women has been shown to have a worsened sleep than males [9]. Shanghai complete lockdown was a unique setting for studying sleep related behaviors. It lasted 2 months and continued for several months with intermittent opening-closing of public places and sport facilities, and suspension of sport events. Universities and other large communities were locked when some positive cases were found. Stritch confinements in dormitories and limited mobility, were applied. University students has been especially affected by lockdowns because of the tightest restrictions in the campus, in comparison with the outside environment. Tongji University has a large College of Football, which enrolls both professional (dual career), semi-professional and student players, which were double affected by the restrictions: as students and as players. This fact can have altered players mood and thus influenced sleep habits. A study performed during lockdown in England on high level athletes, showed that during lockdown 20% of the dual-career athletes adopted a negative coping strategy with the lockdown measures [11].

There is some evidence among professional soccer players that males have a better sleep quality than women during the isolation period [9]. However, also in normal life conditions, sleep disturbances in females’ soccer players has been only recently studied [5], showing a high incidence of sleep disturbance associated with the night pre-game [12], post-game or post training [13] with a decrease in sleep time in those conditions. Female sleep has been shown also to be sensitive to menstrual cycle [14] which in turn affect arousal control, stress response, and memory consolidation [14]. From the response of a survey in 231 woman (non-athletes, 18–28 years old), it was revealed that during lockdown, the habit of going to bed at night after 12 P.M was significantly increased [15] and was associated with disturbances in menstrual cycle. Another study performed in lockdown condition in China on 2084 university students, reported 10% higher rates of sleep disorders in females than male students. Females, also experienced a higher incidence of mental disorders having as a mediating factor sleep [16]. However, findings in male/female differences are controversial in different sports. A study in 146 top Brazilian Olympic athletes of various sport showed worse sleep (measured with polysomnography) in man than in woman [17], however this study didn’t investigate soccer players. The same study showed that 36% of all athletes had a sleep disorder with a greater reduction in sleep quality in men than in women. Female athletes can also show a higher increase in inflammatory biomarkers and an higher fasting insulin levels subsequently to sleep disturbances in comparison to males [18]. Female athletes also showed higher circulating cortisol (which is known to increase as a response to sleep loss) after sleep deprivation than non-athlete females [19]. In another study comparing professional and Olympic athletes, was found that Olympic athletes has less disturbances than recreational athletes, but in the sample weren’t professional soccer players [20]. Daytime sleepiness was found in 22.5% of a sample of 111 Qatar male professional players (ESS>8) [21]. Data on sleep after a prolonged lockdown in professional players are becoming available [9,10] but at our knowledge any data exist on daytime sleepiness in “normal” life conditions and during and after a lockdown in Asian male and female soccer athletes of different level of qualification. Thus, aims of this study was to compare differences in daytime sleepiness between genders and qualification levels in Chinese soccer players of different level of qualification under 0 Covid policy restrictions in the urban area of Shanghai.

2. Methods

Epworth sleepiness scale (ESS) is an 8 items clinical scale commonly used for the measure of sleepiness [22,23] and has been extensively used in different cultural contexts [24,25], and in clinical and sport populations [26]. It has the advantage of being easily administrable, to have extensive normative references [27], and to be available in several languages [28,29,30,31]. The ESS was validated also for Chinese language [32,33]. It comprises 8 items asking how the subject feel sleepy in different daily living activities concerning life situations while a person can feel sleepiness during the day, can be answered in a 0-3 scale [32]. The ESS shown to be stable in time across a period of one year [34] and consistent with other questionnaires for sleepiness [35]. A score of > 8 in the ESS is the threshold for the diagnosis of daytime sleepiness [3].

The ESS questionnaire was submitted online. Subjects were recruited by mean of University offices and after with the social media Wechat and by direct contact and were asked to fill the Chinese version of the questionnaire built in the Chinese social media Wechat (Tencent Technologies, Shenzen, China) [36]. Wechat has proven to be a valuable tool to submit online questionnaires and in China is used by everyone [37]. The questionnaires were filled by soccer students (SS), semi-professional (SP) and professional players (PP) in the city of Shanghai in the weeks 16 to 31 October 2022, after a 10 days complete lockdown in the universities and with still ongoing limitation to mobility. Shanghai experienced a complete lockdown from 28 of March till 30 of May 2022. All the subjects, including the professional players, were also university students. Players’ levels were defined according to the rules of CFA (Chinese Football Association), which are complex, but guarantee a tight classification because are grounded in several performance parameters (e.g., number of games in one year in the division) and on the career of the player. SS were students in the International College of Football of Tongji University and participate in soccer training at least four times per week plus an inter-university weekend match, while SP and PP trained once per day, SP play a regional match every weekend, and PP play a match every 4 days, and sometime twice per week in the major Chinese League. The measures were performed during the championships season. The study was conducted according to the guidelines of the Declaration of Helsinki, and approved by the Ethics Committee of Tongji University (approval code: tjdxsr029). Informed consent was obtained by the participants, after the explanation of the aim of the study.

Gender and level comparisons was performed using One way ANOVA (Scheffe post-hoc) with SPSS v.20.0 and significance level was set a 0.5. Post-hoc statistical power with an MDE (minimum detectable effect) of 0.5, was calculated at 0,9732.

3. Results

A total of 491 soccer players, 441 male and 50 females filled the questionnaire. Mean age for the total group was 19,16±2,68 years (19,17±3,41 for males and 19.10±1.68 for females. 407 were soccer collegiate students (SS), 55 were semi-professional (SP, Level 1 and 2 CFA) and 29 were professional players, playing in the Chinese major league (PP). Among females, 21 were SS and 29 SP players, among males, 386 were SS and 56 SP players. Data were all normal distributed at Kolmogorov-Smirnoff test. Descriptive statistics are summarized in Table 1.

Age was significantly different between levels (F _2,490 = 361,42 p = ,000) but not between gender in each group. Four items of the Epworth scale were find different between males and females. Females declared to feel sleepier in the following items: “sleeping while sitting and reading” (F_1,490 = 9,76, p = 0,002) and while watching television/mobile (F = 11,88, p = 0,001), “sitting and talking with someone” (F_1,490 = 11,22. P =0,001); “sitting quietly after a lunch without alcohol” (F_1,490 = 13, p= 000). Total score was also significantly different between the genders (F_1,490 = 11,12, p= 0,001). All the items (F_2,490= 33,11 – 70,88, p = .000) and the total score (F_2,490 = 13,36 p = 0,000) were significantly different between the 3 levels of qualification. Also, all the items refers to indoor situation, albeit ESS has also item referring to external environmental settings.

The percentages of subjects over the daytime threshold sleepiness (ESS > 8) were: SP females (72%); SP males (65,38%); SS females (52%); SS males (41,6%). The overall SP group (male and females) showed a 69,09% of subject over threshold and the overall SS group 42%. In the overall group females showed the higher % of subject over threshold (64%) while males had 43,20% above the threshold for sleepiness. We found a percent of above threshold sleepiness subjects in SP dramatically higher than those found in a sample of professional players in Qatar 22.5% (ESS>8) [21].

4. Discussion

Surprisingly, in the lockdown condition our sample of male’s professional players show a very low score of daytime sleepiness contrary to what reported in most of the literature we reviewed for western soccer players in normal conditions [3,4,5,17]. However, no data exist about sleepiness in Chinese soccer players in “normal” life conditions to compare. The Epworth scale items results reflect the confinement conditions, referring to all indoor environments. We can hypothesize a cause can be the higher arousal in these athletes caused by intensive training and playing, or to genetic factors, e.g., subjects with less sleepiness has more chance to reach the top level. However, at our knowledge this is the first study in Chinese professional players, and the cultural differences can also play a role in explaining the sleep behaviors. In respect to lockdown conditions, we can hypothesize professional athletes had more disciplined and lived a regular life, while students were more stressed by lockdown measures. Our study was performed during the Shanghai lockdown, with still some restrictive measures going on. In the same period of filling the questionnaire, the university students and players were locked in their dormitories for 10 days. This factor can have influenced the results, increasing the stress levels and thus the sleepiness of the students. Daytime sleepiness has been also related to depression [38], and this is the case of lockdown. In a large sample of children and adolescent the impact of lockdown on mental health has been shown to be dramatic [39]. However, social support was shown to play an important role in reducing the negative effect of lockdown on mental health in 675 non-professional soccer players in China [39], albeit this sample was not investigated for sleep. Cultural differences can also play a role. In Chinese culture, students’ study is highly valued and the competition high, so students may show hopelessness for poor academic performance caused by the lockdown [40].

Despite the controversial literature about sleep disturbances in females’ athletes [11,12,13,17] our results support the presence of a higher percent of sleepiness in female soccer players compared to males. This result is consistent with another study in Spanish professional football players performed during a lockdown, who showed men having better sleep quality than women during the isolation period [9]. However, this latter study didn’t consider daytime sleepiness.

Sleep is an emerging as a key factor for health of female players, and it was indicated among the factors to be improved to increase female soccer players health [41]. It remains a question why females are so dramatically affected by sleepiness in comparison to males, due that training status should different and adapted. One hypothesis which is consistent with the available literature is dual career female athletes faces more challenges than males [42] both socially than physically, and the demands faced by players increases as their level of education/vocation becomes higher. This factor can explain the differences we found in sleepiness between males and females SP players.

We can also hypothesize the training methods for soccer are traditionally developed for men and are less suitable for women, and this can cause a training overload in females, which deals to poor sleep. In fact, as mismatch between coaches and players evaluation of training loads has been showed in professional males soccer players [43] and can be a causal factor of poor sleep, even if no such studies exist in females. Also, psychological reasons (more involvement in their role by females) can affect this outcome: professional female soccer players, show higher values for stress control, motivation, mental ability, and team cohesion in comparison to female amateur [44] which can make them more susceptible of emotional distress. Females’ soccer players were found more sensitive to performance evaluation by coaches and peers [32] and more at risk for anxiety and depression than males [45] and to have shorter sleep-in comparison to other professional’s sport female athletes [46]. In normal conditions, the sleep disruption is likely to be caused by the high physical and mental loads experienced during soccer games [47]. Sleep modification in normal conditions shows an association of deep and REM sleep with fatigue with increased restoring sleep two to three days after match an a pre-match reduction in sleep length [47]. Our results are also consistent with another study, who showed in Italian female professional soccer players in lockdown an increase in depressive symptoms and a sleep worsening [48]. Interactions between coach/trainer and player were more frequent (i.e, daily) among professional (27%) than amateur (11%) and semipro (17%) players during lockdown [49]. This factor can also influenced mood and thus sleepiness in PP. Another factor we didn’t investigated, and that can have influenced the results, is the chronotype of the athletes, or the preference for morning or evening activities. In fact, it has been shown that athletes tended to select and pursue sports that suited their chronotype [50].

5. Conclusions

Due to the exceptional conditions of this study, we observed different behaviors in soccer players from previous studies on daytime sleepiness. However, our study focused on Chinese soccer players during an unusual life condition, and no data existed previously in such experimental conditions. Professional soccer players showed a very low score in daytime sleepiness, and this could be explained with the more organized life they had during the lockdown. Commitment to result can have reduced the impact of emotional stressor in professional soccer players. We can also hypothesize the subjects with a higher arousal reach the top level, or the intensive training and playing in professional make them less sleepy through the activation of hypothalamic-surrenal axis. Our result confirm females more susceptible to sleep disturbances than males even in the lockdown conditions. Due to the exceptional experimental conditions of the present study (Shanghai lockdown) we can hypothesize the excessive sleepiness in recreational and semiprofessional soccer players could be linked to the daily life restrictions and consequent mood disturbance, while these conditions seemed to affect less the professional players who benefit of better life arrangements. Cultural differences could also explain the observed reduced sleepiness in professional Chinese soccer players in comparison to Western players.

Beside these findings, the results suggest than interventions are necessary to improve the sleep hygiene in SP soccer players, especially in females. Further investigations are necessary on the low sleepiness of professional soccer players, e.g., a study performed in non-emergency conditions. A limit of our study is we don’t have any data about sleepiness before lockdown and we didn’t measure any physiological data (e.g., circulating cortisol, inflammatory biomarkers an menstrual cycle) to correlate with the questionnaire. Also, a measurement of depression could have been helpful in better understanding the results. A follow-up measurement after the recovering of normal life, will be also necessary. Also, we missed a group of professional females’ athletes to compare with males professionals. Shanghai lockdown was a unique setting to study the sleepiness in soccer players. The observed modification in sleepiness behaviors can be useful for the adoption of measure to increase soccer players health and well-being, especially in female soccer players.