Coronavirus disease 2019 is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), it is a serious infectious disease with cough, fever, and fatigue as its main clinical manifestations [65–66]. SARS-CoV-2 has been designated a global disease epidemic by the World Health Organization [67]. Coronavirus disease 2019 has negatively affected individual physical and psychological health [68–70]. Numerous empirical studies further support those adverse effects impact athletes’ mood and sleep quality [71], but may also lead to poor athletic performance [72]. In addition, an array of recent studies has shown that the COVID-19 pandemic has adversely affected sleep quality in athletes, introducing health risks related to poor sleep [73]. Therefore, it is essential to study the impact of COVID-19 pandemic restrictions on athletes’ sleep quality.
Sleep is one of the basic needs of human beings for survival and development. Poor sleep quality has become an especially common problem for athletes [1, 2]. The reason might be that athletes experience many stressors such as high training loads, competition demands, early morning training, and altitude exposure [3, 4]. These stressors from training and competition make their lives different from those of ordinary people [5]. Additionally, often athletes cannot obtain a consistent 7–9 hours of recommended adult night sleep time [6]. As such, athletes’ sleep quality may be sub-optimal compared to that of the general population. Studies [3, 7] have shown that athletes often have sleep-related problems during competitions, such as insomnia symptoms, poor sleep quality, sleep difficulties, and daytime sleepiness [5, 8, 9]. Prior studies also showed that sleep is crucial for athletes’ daily recovery and performance [10], and good sleep quality is the basis of good athletic performance. Sleep is also a key factor in maintaining athletes’ mental health [11, 12].
Thus, it is important to know the risk factors contributing to poor sleep quality in athletes. One of the possible risk factors is perceived stress. Perceived stress refers to an individual's cognitive evaluation that determines the impact of an "objective" stressor on individuals [13]. According to the theory of sleep disturbance, stressful events can disturb normal sleep processes and affect the quality of sleep [14]. Research indicates that there is a close connection between perceived stress and poor sleep quality [15, 16] such that the higher the level of perceived stress, the worse the sleep quality [17–19].
For athletes, empirical studies also found that perceived stress was positively associated with poor sleep quality [20, 21]. The stress process model posits that stress not only directly but also indirectly affects the individual by reducing psychological resources [22, 23]. The indirect relationship between perceived stress and sleep quality in athletes, however, remains unclear.
Therefore, this study explores the direct and indirect links between perceived stress and sleep quality in athletes to better understand how perceived stress relates to sleep quality. Based on prior studies [24], we examined the potential mediating effects of competitive state anxiety and depression as they relate to sleep.
Anxiety is defined as an aversive motivational state that occurs in threatening situations [25]. Anxiety can induce changes and result in poor athletic performance [26–29]. State anxiety is a temporary state of unease that arises in certain situations such as sports competition, which is one of the key factors influencing sports performance [30–32]. According to the cognitive theory of emotion [33], anxiety arises when individuals are stressed. Previous studies have shown that there is a significant positive correlation between perceived stress and sleep quality [34–36]. Likewise, studies found that competitive state anxiety was positively related to athletes’ poor sleep quality [37]. As a result, it can be inferred that competitive state anxiety may be a mediating variable in the association between perceived stress and athletes’ sleep quality.
Depression is another important risk factor. It has become the second most common disease in humans as of 2020 [38]. Depression is also a common psychological problem among athletes [39, 40]. Some studies found, for example that athletes have a higher level of depression than the general population [41]. According to the diathesis-stress model, stress can lead to a series of negative health outcomes including depression [42]. Statistics showed that nearly 70% of primary depression is caused by stress. The role of stress in the onset of depression accounts for 20–50% [43, 44]. Also, many empirical studies have confirmed that there is a positive correlation between perceived stress and depression [45–47]. In addition, according to the cognitive model of insomnia [48], individuals who experience depression tend to selectively pay attention to stressful external events and apply cognitive biases. When they detect sleep threats or experience lack of sleep, they will further engage in negative cognition and false beliefs, eventually leading to sleep loss or even, in the long-term, sleep disorders. Studies have confirmed that depressed individuals have more difficulty in falling asleep and have worse sleep quality [49–51]. In this case, depression may be a mediating variable in the relationship between perceived stress and poor sleep quality.
The Present Study
Considering the above, we investigated the influence of perceived stress on athletes' sleep quality during COVID-19 in China. Overall, our goal was to examine the relations between perceived stress, competitive state anxiety, depression, and sleep quality in Chinese athletes. Based on the above literature, we proposed the following hypotheses: (H1) perceived stress is positively associated with poor sleep quality; (H2) competitive state anxiety mediates the correlation between perceived stress and sleep quality; and (H3) depression mediates the correlation between perceived stress and sleep quality.