We contacted 5 professional teams to participate in the study from August to December 2019. A description of the study was provided to prospective participants after which voluntary consent was obtained. All tests were conducted in each team’s living headquarters. Fifty-five males (average age, 20.41 ± 2.40 years; age range, 16–25 years) participated in study 1. Thirty-four Korean elite esports athletes playing in professional leagues were compared to 21 age- and sex-matched nonathletes. Participants under treatment for sleep disorders and those suffering from other psychiatric disorders were excluded as determined by their medical histories and prior phone interviews. Ethics approval was obtained from Sungshin Women’s University Institutional Review Board (No. of Approval: SSWUIRB 2019-030-001).

The current study examined two weeks of sleep patterns for all participants. Self-report questionnaires were conducted at baseline, and all subjects were asked to record sleep diaries for 2 weeks. After 2 weeks of sleep monitoring, participants were provided with brief individual feedback for compensation.

Data were analyzed using the Statistical Package for the Social Sciences (SPSS) version 25.0 (IBM Corp., Armonk, NY, USA). Descriptive statistics including means and standard deviations were used to summarize variables. For data composed of continuous variables, t-test or analysis of variance was used, and for the response rate, a chi-square test was used.

Thirty-four esports athletes of two major esports genres in Korea [Multiplayer Online Battle Arena (MOBA) and First Person Shooter (FPS)] were recruited from a total of five professional teams. They were all males who played an average of 13.56 (± 1.63) hours per day. The mean age difference between the esports athlete group (20.41 ± 2.40 years) and nonathlete group (21.95 ± 2.92 years) was not significant. There were 3 adolescents included in the esports athlete group, but no adolescents in the control group. There were also no differences in their body mass index and caffeine consumption. Demographic information can be found in Table 1.

Sleep characteristics of esports athletes derived from the sleep diaries were as follows: the mean TST of esports athletes was 436 (± 73) minutes, which was 27 minutes longer than that in the nonathlete group, but there was no significant difference. The average BT of esports athletes was 4:04 a.m., which was significantly later than that of nonathletes at 2:18 a.m. (t = 5.588, p < 0.001). Lights off (t = 4.887, p < 0.001) and SO (t = 6.026, p < 0.001) times of esports athletes were also significantly later than the average times for the nonathlete group. The number of awakening of esports athletes was 1.25 (± 1.71) times on average during sleep, and the average WASO time was 12.39 (± 21.80) minutes; both results were not significantly different from those of nonathletes (Table 2). The average WT of esports athletes was 12:13 p.m. (± 47 minutes), which was significantly more delayed than that of the nonathletes (10:09 ± 89 minutes; t = 6.681, p < 0.001), and the TOB after awakening among esports athletes was also delayed by more than two hours compared with the nonathletes (t = 7.028, p < 0.001). The SQ (t = -3.156, p < 0.001), which was measured on a 5-point Likert scale, and the FR (t = -2.857, p < 0.001) of esports athlete group were rated significantly lower than the nonathlete group.

Information from self-report questionnaires is presented in Table 3. There were no significant differences in either the severity of insomnia or daytime sleepiness among esports athletes and nonathletes. However, the mean daytime sleepiness score among esports players exceeded the cut-off (15 points), indicating that esports athletes experienced high levels of sleepiness during the day. Esports athletes scored significantly higher in depression (t = 3.818, p < 0.01), with a higher proportion of esports athletes scoring above the clinical cut-off value (CES-D > 16) for depression than the proportion of nonathletes (64.7% vs. 14.3%, p < 0.001). However, the levels of anxiety (STAI-X-1) and perceived stress (Perceived Stress Scale) among esports athletes were not significantly different from those among nonathletes. The scores of the sleep quiz, which measures general knowledge about sleep, were significantly lower in esports players than in nonathletes (46.35 vs. 55.93, respectively; p < 0.01).

Three volunteers from the participants of study 1 and three of their coaches attended the study 2 underwent the semi-structured interview. We reviewed the baseline questionnaires, which described their experiences and thoughts, examined the esports athletes’ sleep patterns and asked additional questions. In the process of organizing the questions, the questionnaire used in an existing phenomenological qualitative study of sleep disorders was referenced [23]. Interview instructions were developed, and the interviews were supervised by a clinical psychologist who is also a behavioral sleep medicine specialist.

Each of the questions presented in the interview addressed particular topics or areas including health conditions, relationship, work, and life as an esports athlete, and sleep. Some examples of the seed questions used to prompt the interviews can be seen in Table 4. The progression of the questions was not equivalent for all participants and varied based on interviews and participants’ responses. However, based on the interview instructions, researchers could gather similar forms of information from all participants. In this way, researchers could save time and decrease the collection of unnecessary information compared with unstructured interviews [24]. Researchers could create or add questions even if they were not included in the guidelines [25]. In this study, the analysis method of Giorgi [26] was used to explore the meaning and nature of risk factors associated with sleep patterns of esports athletes. The stages of analysis method based on Giorgi are: 1) read the description for the sense of the whole, 2) divide the description into meaning unit, 3) transform meaning units into best disciplinary expression, 4) synthesize transformed meaning units into structure. NVivo12 (QSR International, Melbourne, Australia) was used to analyze the qualitative data.

Six sleep risk factors were identified in the interviews with esports athletes. The esports athletes display delayed sleep phases due to their training time, which usually ends very late at night, with one participant reporting “individual training continues until 3 a.m. after completing team training at midnight.” The athletes and their teams insisted that this time frame was necessary to make the training more efficient. In addition, the sleep environment of the shared headquarters, such as the room temperature, outdoor noise, absence of a health management system, use of the wrong methods to improve sleep quality, and time difference due to away matches were also considered sleep risk factors. The interviewees also considered the tension of the night before a competition, long exposure to light, stress, and caffeinecontaining drinks as sleep risk factors.

Because all the participants from study 1 participated in a sleep education and a feedback session, the effects of those interventions have already been included in the protective factors. Knowledge about the environment that improves sleep quality, proper actions for better sleep quality, and sleep hygiene were identified as protective factors that had a positive effect on sleep quality. Strategies such as having a more organized lifestyle, improving sleep hygiene, not napping during the daytime, and not using smartphones for more than 30 minutes before going to bed can also improve athletes’ sleep quality.

Stress can have a (negative) effect on mental health and sleep quality. Various factors such as fear of the future due to job instability, lack of social support, and competition for the starting line-up (which can cause short-term depression) can cause stress among esports athletes. These factors can cause short-term depression. In addition, personality differences and communication problems with teammates of different nationalities can also cause stress among athletes.

Esports athletes were usually students before they started their careers, with most athletes choosing to drop out of school to become esports athletes. Most of the athletes experienced opposition from their families, but the level of support from their families was dependent on the success of their careers. The majority of the top-tier (popular) athletes had high job satisfaction, and they were proud of their careers. Esports athletes had pride that they had fans and felt responsible for meeting their fans’ expectations. In addition, the athletes experienced emotional distress from criticism on social media; furthermore, the atmosphere of the team not only affected the outcome of the game but also the duration of internal team conflicts.

Team management was deeply related to both mental health and sleep problems of esports athletes. Few esports teams have an organized management system or a sufficient number of professional managers. Team management seemed to be heavily affected by the head company’s capacity and budget. The role of the team directors and coaches who manage young esports athletes is critical. However, they often lack the professional skills to manage the organization, such as managing conflicts between the athletes. Coaches need to be able to help athletes who are having a difficult time with consultation and proper rest and need to teach them how to deal with criticism with a more flexible mindset.

The need for intervention was mainly mentioned by the coaches. There were demands for education in communication skills, emotional management skills, and sleep improvement programs including psychological counseling. Improving awareness of the importance of good sleep has been addressed as the most helpful factor in sleep improvement programs. It was also suggested that educational methods are needed to suit the athletes’ learning abilities. For an intervention to be effective, a rather strong level of recommendation is required, and a system that can be enforced may be needed. The esports athletes thought that psychological counseling was essential and felt that it would be helpful to talk to outside experts about topics that were difficult to discuss with their managers, coaches, or teammates. Communication problems within the team were the most frequently mentioned issues by the coaches, and the need for intervention was emphasized. The causes of communication problems appeared to be that most athletes are young, lack sufficient school education, tend to display some self-centered qualities, and do not have sufficient social skills to resolve conflicts.

In this study, the mean TST was 7.26 (± 1.21) hours, which was not significantly different from the control group. However, this appears to be significantly lower than mean TSTs of esports athletes in other countries. In previous studies, 8.1 (± 1.2) hours sleep in the US [27] and 7.8 (± 1.3) hours in Germany [28] were reported. Considering that adolescents in East Asia (especially in Korea) sleep less than those in the US and European countries [29], it is worthy not only to compare them with the general population in Korea but also to esports athletes from other countries.

The delay in sleep phase of esports athletes seems to be primarily affected by their environment and training schedule. Almost every esports athlete lives in shared headquarters with his or her teammates, and they train together. One of the most important parts of team training is practicing matches with other teams (i.e., scrimmage), which makes it difficult to change sleep schedules. In addition, prolonged use of computers for training (and the use of smartphones before bedtime) delays their sleep timing and makes it difficult for athletes to fall asleep at a normal bedtime.

Esports athletes also reported significantly worse sleep quality compared to their nonathlete counterparts. There are two plausible explanations for this difference. First, qualitative evidence from the present study suggests that some esports athletes may be exposed to environmental factors that disturb sleep (e.g., snoring), leading to a deterioration in subjective sleep quality. Evidence indicates that the sleep environment is strongly linked with adequate sleep quality [30]. One noteworthy implication of this finding is that if a team lives in a shared headquarters, as was the case in our study, then presumably an entire team may be at risk of poor sleep quality if the sleep environment is suboptimal. In addition to sleep environment, poor sleep quality and not feeling refreshed after awakening in the esports athlete group may have been influenced by high levels of depression. Sleep quality is known to be highly correlated with depressive symptoms and stress [31,32]. In this study, the perceived stress level reported by esports athletes was not significantly higher than that of the nonathletes. However, the findings that the average depression score exceeded the clinical cut-off value of 16 and that the rate of the high-risk group for depression reached 64.7% suggests a high possibility that depression worsened the subjective sleep quality of esports athletes. These high levels of depression are also related to the delayed sleep phase [33]. In a study that examined the relationships among sleep quality, circadian pattern, and emotion in 236 young adults aged approximately 18 years, participants with an evening phase complained of more depressive symptoms [33].

In addition to delayed sleep, our qualitative findings have shown various risk factors for poor sleep in esports athletes. Poor sleep knowledge can act as a perpetuating factor in sleep problems. In the sleep knowledge questionnaire, the average score of the esports athlete group was significantly lower than that of the nonathlete group. Based on misinformation and irrational beliefs, some of the athletes maintained typical persistent behaviors, such as intense training before bedtime [3] or drinking alcohol before bedtime. This suggests that sleep interventions, such as sleep hygiene, may also help improve sleep in this group. In fact, a recent study showed that sleep hygiene education alone helped improve sleep in low socioeconomic groups [34,35].

Another problem found through qualitative research was the lack of communication skills among the players. Individuals participating in the interviews of the study 2 reported that most esports athletes are young, are not well-educated, and lack sufficient social skills to resolve conflicts. Despite the importance of teamwork and communication skills in this team sport [36], spending long hours without direct personal contact with other individuals outside of the game may result in limited growth of social skills. Insufficient social skills affect not only daily life but also competition performance, and because most of the athletes’ time is spent with teammates, their social relationships can have a significant impact on game performance [37]. Furthermore, communication quality may be affected not only by individuals’ communication skills but also by their sleep quality. Players with sub-optimal sleep appear more likely to be emotionally sensitive to negative comments from team members and coaches regarding their performance [38]. Stress is itself a risk factor for poor sleep, but a lack of social support, such as that from family and friends, derived from qualitative research is also an important variable to be addressed. Social support is a protective factor that allows individuals to maintain a sense of wellbeing in stressful situations [39]. Even if stress-coping skills are insufficient, mental health can be maintained if social support is sufficient [40].

The role of the organization is important in reducing the stress of esports players. Our results show that esports athletes’ stress levels are greatly influenced by the policies and capabilities of their organizations and managers because they live in a group together. Players mainly reported stress factors such as the burden of the game, anxiety due to an uncertain future, competition for the starting lineup, relationships with their team members, and lack of social support due to camp life. These psychosocial stressors not only reduce sleep quality [41] but can also cause sleep problems [42-45]. In particular, relationships with other team members are often worsened in the course of receiving feedback on the game, which may be the reason that the athletes did not have the opportunity to develop sufficient emotional control skills or social skills, including communication skills. As a result, coaches must intervene in players’ conflict situations, but they do not have expertise in conflict mediation or psychological counseling; therefore, the effectiveness of their intervention cannot be guaranteed.

Physical environmental conditions are also directly related to the organization’s management capabilities. Sleep hygiene is known to be a protective factor affecting bedtime, sleep latency, and total sleep time [46]. Sleep hygiene is related to several areas of sleep, including behavioral, physiological, and emotional arousal, the sleep environment, and sleep stability [47]. A recent qualitative study on the performance of esports athletes identified a weakness in their emotional regulation ability, lack of trust between peers, and inefficient communication as factors that hinder them from achieving good performance [48]. This is consistent with the qualitative results of this study.

This study has some limitations. First, whilst sleep diaries are considered superior to other forms of self-report (e.g., due to reduced memory bias [49]), it would have been valuable to simultaneously obtain objective sleep data (i.e., wrist actigraphy). Second, sufficient quantitative data on risk factors for poor sleep were not collected. Because specific information on predictable factors, such as caffeine use, smoking, and the timing of smartphone use before bedtime, has not been identified, the relationship between these factors and actual sleep was not confirmed statistically. In follow-up studies, the effect size of risk factors for poor sleep could be additionally identified through the collection of detailed information on such life variables.

The current study is the first empirical study to evaluate the sleep of Korean esports athletes. Considering the rapidly growing esports industry, research on the mental health of esports players is crucial. The present study can provide a good reference for future researchers exploring this field. Although it was limited to exploratory research, there are various implications for clinical interventions related to the sleep of esports players. A wide range of interventions including sleep education tailored to the level of esports athletes, cognitive behavioral therapy for insomnia (CBTi), social skills training, emotional management, and stress reduction programs should be developed and implemented on both individual and organizational levels.