Introduction

It is estimated that humans spend approximately one-third of their lives sleeping, which is essential for maintaining their physical and mental health1.Sleep deprivation and poor sleep quality have become a pressing concern as the 2022 China Sleep Research Report reveals that 64.75 percent of citizens sleep less than eight hours per day and an increasing number of individuals are experiencing sleep issues2. In recent years, college students' sleep issues have become more widespread. They often experience high levels of psychological and academic stress, which may affect their sleep habits and quality3,4. For example, Chen et al. found that there was a sharp rise in the overall prevalence of sleep problems among Chinese college students between 2010 and 2020 (23.5%)5. Sleep quality is typically defined as difficulty falling asleep or staying asleep and the frequency of nighttime awakenings6. A number of psychological problems, such as anxiety, sadness7, anger8, and suicidal ideation9, are closely related to poor sleep quality. Overall, previous research on sleep quality has paid less attention to college students and focused more on adolescents, chronic insomnia and depression groups10,11,12,13,14,15. It is particularly noteworthy that since the COVID-19 outbreak, the sleep quality of college students has dramatically deteriorated, and the prevalence of sleep problems has increased compared to before the outbreak16,17. In addition, numerous intervention studies have demonstrated that mindfulness training can significantly improve sleep quality18,19,20. Furthermore, the mechanisms underlying the influence of mindfulness on sleep quality need to be explored21,22. The results of the current study will provide insights into the mechanisms by which mindfulness influences sleep quality, which may contribute to the development of new treatments for sleep disorders.

Mindfulness and sleep quality

Mindfulness is often defined as a state of non-reactive, non-judgmental, and present-focused awareness, in which every thought, feeling, or sensation is recognized and embraced just as it is23,24. Mindfulness can refer to both a trait, known as trait mindfulness, and a state, known as state mindfulness. Trait mindfulness is a naturally occurring level of mindfulness across individuals, characterized by qualities such as attention, openness, and curiosity. State mindfulness, on the other hand, is a state formed or sustained through attentional regulation, such as mindfulness practice interventions. Research suggests that compared to state mindfulness, which arises depending on specific situations, trait mindfulness functions as a stable trait of an individual. This trait not only allows individuals to perceive the world in a less patterned manner but also enables them to maintain this open-mindedness in their daily lives25, providing a prerequisite for improving sleep quality. Studies have found that even without intervention or intentional enhancement of mindfulness skills, trait mindfulness is prevalent among populations26. Since the subjects of this study did not undergo specific mindfulness interventions, mindfulness refers to trait mindfulness. A meta-analysis has shown that mindfulness training can improve sleep quality27.Furthermore, empirical studies showed that mindfulness is negatively associated with sleep quality28,29,30; mindfulness improves sleep quality by alleviating sleep problems through interventions in cognitive processes, such as MBCT therapy20. This result has been confirmed in various populations (e.g., patients with sleep disorders, the elderly with chronic insomnia, prisoners, etc.)10,11, 31. Previous studies have shown that the most important predisposing cause of insomnia is the natural triggering of negative emotions or thoughts just before bedtime32. Negative emotions before bedtime lead to irrational rumination33, which promotes the overarousal of negative emotions and makes it difficult to fall asleep. Research has found that mindfulness-based interventions positively influence mood regulation34. Besides, the emotion regulation model of mindfulness states that mindfulness influences attentional allocation during emotion regulation, causing people to focus more on awareness and avoid automatic responses to identified thoughts and emotions35, resulting in people being better able to cope with negative emotions. These studies suggest that mindfulness may be a significant factor in sleep quality. Therefore, the current study hypothesizes that mindfulness would be positively associated with sleep quality (H1).

The mediating role of self-control

Self-control is defined as “the self-initiated control over one's ideas, feelings, and behavior when permanently valued goals conflict with temporarily more satisfying goals”36. First, mindfulness can significantly positively predict self-control37,38. Numerous studies have demonstrated that increased levels of mindfulness can facilitate improved self-regulation, enhance a person's ability to control attention and emotion regulation39, suppress impulsive behavior, and thereby increase a person's level of self-control40,41,42. Empirical research findings also indicate that mindfulness contributes to reducing negative emotions such as anxiety, depression, and stress43, while promoting positive emotions44. This is conducive to enhancing individuals' cognitive resource allocation function, thereby achieving self-control in behavior45. Broderick and Jennings (2013) also found from a neurophysiological perspective that mindfulness can offset the depletion of self-control resources, thereby enhancing individuals' level of self-control. Therefore, mindfulness may positively predict individuals' level of self-control46. Second, self-control may significantly negatively predict a person's sleep quality20,47. Poor self-control has been shown to make it more difficult for individuals to resist temptations and may lead to a higher likelihood of sleep problems, ultimately resulting in lower sleep quality47,48. Conversely, higher self-control ability is conducive to cultivating good sleep habits (e.g., increasing sleep duration and reducing daytime fatigue), which improves sleep quality49,50. Therefore, the current study hypothesizes that self-control would mediate the relationship between mindfulness and sleep quality(H2).

The mediating role of bed procrastination

Bed procrastination is the phenomenon of a person staying up later than planned for no external reason51. First, mindfulness can negatively predict bed procrastination22. In the research on general procrastination behavior, the short-term reparation theory posits that procrastination is an act where individuals yield to repairing negative emotions and consequently forsake positive long-term outcomes52,53. Mindfulness has been found to have a positive impact on individuals' emotion regulation abilities54, suggesting that higher levels of mindfulness can result in reduced procrastination behavior. Empirical studies have already demonstrated successful cases of using mindfulness training to intervene in procrastination behavior55,56. Considering bed procrastination as a specific form of procrastination, which exhibits a high correlation and similar psychological mechanisms to general procrastination behavior57, mindfulness may influence sleep quality by reducing bed procrastination behavior. Second, the degree of bed procrastination significantly positively predicts sleep quality58. The procrastination-health model indicates that procrastination is a major risk factor for poor sleep quality59. Studies indicate that bed procrastination is a major cause of inadequate sleep57,60 and that bed procrastination leads to sleep deprivation51 and exacerbates individual fatigue57,61.Therefore, the current study hypothesizes that bed procrastination would mediate the relationship between mindfulness and sleep quality(H3).

The sequentially mediating effects of self-control and bed procrastination

In the context of the strength model of self-control, which posits that individuals require a certain level of cognitive resources to counteract ingrained impulses and regulate their attention, emotions, and behaviors, self-control emerges as a pivotal factor influencing procrastination behavior62. According to this model, depletion of psychological resources increases the likelihood of self-control failure63. Consequently, procrastination can be viewed as a manifestation of self-control deficits57. Specifically, individuals with diminished self-control may struggle to resist external temptations, leading to delays in bedtime routines and subsequent disruptions in sleep quality50. However, it is important to acknowledge that self-control alone may not entirely account for procrastination tendencies or sleep outcomes. While self-control undoubtedly plays a significant role, other factors such as mindfulness may also exert influence. Mindfulness, characterized by non-judgmental awareness of present experiences23,24, has been linked to enhanced self-regulatory abilities and reduced procrastination tendencies64. Therefore, it is plausible to posit that mindfulness could indirectly impact sleep quality by mitigating both self-control depletion and bedtime procrastination. In light of these considerations, it is proposed that self-control and bedtime procrastination function as sequential mediators in the relationship between mindfulness and sleep quality. Specifically, mindfulness may bolster self-control capacities, thereby reducing bedtime procrastination and ultimately improving sleep outcomes. Therefore, this study suggests that self-control and bed procrastination would sequentially mediate between mindfulness and sleep quality (H4).

According to the framework of the Health Behavior Model65, individual factors such as mindfulness and self-control influence behavioral factors such as bed procrastination, which in turn affect health outcomes such as sleep quality. Individual factors encompass traits, attitudes, and beliefs, with mindfulness being an inherent psychological trait that may positively influence sleep quality by improving individuals' psychological states and attitudes. Behavioral factors include individuals' habits and decision-making processes. Both self-control and bed procrastination serve as behavioral habits that regulate individuals' decision-making and behaviors, thereby impacting sleep quality. Mindfulness may indirectly improve sleep quality by enhancing individuals' self-control abilities and reducing bed procrastination behavior.

Overall, we propose a hypothetical model (see Fig. 1). This model describes how sleep quality is affected by mindfulness, self-control and bed procrastination. This study can provide recommendations for improving college students' sleep quality at a practical level and expand the scientific study of factors affecting sleep quality.

Figure 1
figure 1

The hypothesized model.

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Methods

Participants

Drawing upon the methodology of online data collection utilized by previous scholars, we have implemented the online data collection method66.The data used in this study were gathered via a online survey platform, Sojump (wjx. cn) during the ongoing COVID-19 pandemic, from June to July 2021. The participants were 763 undergraduates from two central universities in China. All participants volunteered to participate in this research. The mean age of the subjects was 19.48 years (SD = 2.06). The participants consisted of 427 (56%) freshmen, 84 (11%) sophomores, 226 (29.6%) junior students, and 36 (3.4%) seniors. Of the participants, 270(35.4%) were men and 493 (64.6%) were women. This research was approved by the ethics committee of the corresponding author's institution. G*Power 3.1 was used to calculate post-hoc statistical test power for this investigation67. The G-Power calculation yielded a post-hoc power of 0.95. [Input parameters: Effect size = 0.02(consulting the main effects in Hu et al.)68; α err prob = 0.05].

Measures

Mindfulness

The Mindful Attention Awareness Scale (MAAS), revised by Chen et al.,69 is used to assess mindfulness. This unidimensional scale includes 15 items(e.g.,I rush through activities without being really attentive to them). Responses were given on a 6-point Likert scale (1 = almost always; 6 = almost never). Higher scores indicate higher levels of awareness and attention focused on the present. The Cronbach's alpha of the scale in this study was 0.87.

Self-control

To assess self-control, we used the Self-Control Scale70, which includes 7 items(e.g.,I am good at resisting temptation) and is divided into the subscales of self-discipline and impulse control. Items were rated using a 5-point Likert scale(1 = strongly disagree; 5 = strongly agree). Reverse scoring is used for questions 2, 4, 6, and 7. Higher scores represent higher levels of self-control. The Cronbach's alpha of the scale in this study was 0.71.

Bed procrastination

Bed procrastination was measured using the bed procrastination behavior scale71.This unidimensional scale contains 9 items(e.g.,I go to bed later than I had intended.). The scale was scored on a 6-point Likert scale (1 = almost always; 6 = almost never). Higher scores represent higher levels of bed procrastination. The Cronbach's alpha of the scale in this study was 0.87.

Sleep quality

We adopted the updated scale of the Pittsburgh Sleep Quality Index72, which includes 18 items(e.g., During the past month, when have you usually gone to bed at night?) and is divided into seven dimensions: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbance, use of sleeping medication, and daytime dysfunction. Each component is given a value between 0 and 3; the sum of the values of all components gives the overall sleep quality score. Higher scores represent lower levels of sleep quality. The Cronbach's alpha of the scale in this study was 0.66.

Procedure

The present work was approved by the Ethics Committee of Soochow University. Using the convenience sampling method, participants were given instructions on how to complete the questionnaire before data collection73. Informed consent was obtained from the participants, and their anonymity was emphasized. Each participant had the right to withdraw from the study at any time.

Data analyses

All statistical analyses were performed using SPSS 23.0(Statistical Product and Service Solutions https://www.ibm.com/products/spss-statistics) software. Firstly, descriptive statistics and correlations were conducted. Then, PROCESS macro Model 4 was performed to test the individual mediating roles of self-control and sleep procrastination. Finally, PROCESS macro Model 6 was performed to test the sequentially mediating effects of these two variables.

Ethics declarations

The study was conducted according to the guidelines of the Declaration of Helsinki, and approved by the Academic Ethics and Ethics Committee of Soochow University. Informed consent was obtained from all participants or, if participants are under 18, from a parent and/or legal guardian.

Results

Common method biases

To test for potential common method bias, the current study applied Harman's single-factor analysis was used in the present study in accordance with the suggestions of Podsakoff et al.74.The findings showed that the interpretation rate of the first common factor was 23.98%, indicating that common method bias was unlikely to be a serious problem.

Correlations among the studied variables

Descriptive analysis and correlation analysis showed (see Table 1) that mindfulness was positively correlated with self-control (r = 0.50, p < 0.01) and negatively correlated with bed procrastination (r = –0.40, p < 0.01) and sleep quality (r = – 0.39, p < 0.01). Similarly, self-control was negatively correlated with both bed procrastination (r = – 0.50, p < 0.01) and sleep quality (r = – 0.33, p < 0.01). All the correlations among the research variables are significant, thus meeting the criteria for further mediation analysis.

Table 1 Descriptive and correlation analysis.
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The mediating role of self-control

We used Model 4 of the PROCESS macro75 to test the mediating role of self-control on the relationship between mindfulness and sleep quality, and the results is shown in Fig. 2. Previous research has found that gender, grade and age can affect the sleep quality of college students76,77. Therefore, to enhance the reliability of the data analysis results, we will treat them as control variables. After controlling for gender, age and grade, mindfulness was positively associated with self-control (β = 0.50, t = 15.72, p < 0.001), which in turn was negatively related to sleep quality (β = – 0. 18, t = – 4.69, p < 0.001). The negative direct association between mindfulness and sleep quality remains significant (β = – 0.29, t = – 7.65, p < 0.001). Therefore, self-control partially mediated the relationship between mindfulness and sleep quality (indirect effect = – 0.09, SE = 0.02, 95%CI = [– 0.13, – 0.05]). The mediation effect accounts for 39.13% of the total effect of mindfulness on sleep quality. Thus, Hypotheses 1 and 2 were supported.

Figure 2
figure 2

The mediation model. N = 763. ***p < 0.001. Path coefficients shown above are standardized. The dotted line indicates that the path coefficient is not significant.

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The mediating role of bed procrastination

We used Model 4 of the PROCESS macro75 to test the mediating role of bed procrastination on the relationship between mindfulness and sleep quality, and the results is shown in Fig. 3. After controlling for gender, age and grade, mindfulness was negatively associated with bed procrastination (β = – 0.38, t = – 11.44, p < 0.001), which in turn was negatively related to sleep quality (β = 0.38, t = 11.45, p < 0.001). The negative direct association between mindfulness and sleep quality remains significant (β = – 0.23, t = – 6.93, p < 0.001). Therefore, bed procrastination partially mediated the relationship between mindfulness and sleep quality (indirect effect = – 0.14, SE = 0.02, 95%CI = [– 0.19, – 0.11]). The mediation effect accounts for 60.87% of the total effect of mindfulness and sleep quality. Thus, Hypothesis 3 was supported.

Figure 3
figure 3

The mediation model. N = 763. ***p < 0.001. Path coefficients shown above are standardized. The dotted line indicates that the path coefficient is not significant.

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The multiple mediation analysis

First, model 6 in the Process macro was adopted, and the results of the independent and multiple mediation tests are shown in Table 2, Table 3, and Fig. 4. After controlling for gender, age and grade. The results of regression analysis revealed that mindfulness can significantly and positively predict self-control (β = 0.50, p < 0.001); mindfulness can significantly and negatively predict bed procrastination (β = – 0.18, p < 0.001); self-control can significantly and negatively predict bed procrastination (β = – 0.40, p < 0.001); mindfulness can significantly and negatively predict sleep quality (β = – 0.22, p < 0.001), and bed procrastination can significantly positively predict sleep quality (β = 0.37, p < 0.001), the negative predictive effect of self-control on sleep quality was not significant. Second, the results showed that both the direct prediction of mindfulness on sleep quality and the independent mediation effect of bed procrastination were significant, as shown by the results of the mediation effect analysis using the Bootstrap method (5000 samples). In addition, the chain mediation effect of self-control—bed procrastination was significant. Thus, Hypothesis 4 was supported.

Table 2 Regression analysis of the mediation model between mindfulness and sleep quality in self-control and bed procrastination.
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Table 3 The mediating effects of self-control and bed procrastination on mindfulness and sleep quality.
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Figure 4
figure 4

The multiple mediation model. N = 763. ***p < 0.001. Path coefficients shown above are standardized. The dotted line indicates that the path coefficient is not significant.

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Discussion

In the context of the COVID-19 pandemic, a sequential mediation analysis was conducted in the present study to investigate the psychological mechanisms underlying the relationship between mindfulness and sleep quality. The findings demonstrated that self-control and bed procrastination mediated the relationship between mindfulness and sleep quality. Amidst the COVID-19 pandemic, these findings hold significant practical implications for assisting college students in effectively managing stress, anxiety, and sleep issues.

Mindfulness and sleep quality

The results indicated that mindfulness is associated with sleep quality, which is consistent with previous studies78,79 and supports our hypothesis. First, mindfulness interventions can improve sleep-related maladaptive cognition, so that people face life events with an open and accepting attitude and have fewer negative thoughts. As a result, people sleep better because they perceive life events as more positive80,81,82. In addition, Monitor and Acceptance Theory (MAT) states that the coexistence of attention monitoring and reception can help people with poor sleep quality reduce psychological distress, shorten sleep latency, and thus improve sleep quality83,84. Second, mindfulness can reduce an individual’s depression and anxiety85, improve an individual’s ability to regulate emotions, reduce arousal before bed, and improve sleep quality19. Third, mindfulness can significantly reduce hypothalamic-pituitary-adrenocortical activity86, thereby maintaining a regular sleep–wake rhythm that promotes good sleep87,88. Thus, mindfulness has a positive effect on improving cognitive, emotional, and physiological states, thereby improving the quality of sleep for individuals. Fourth, the results of the meta-analysis indicate that the third-wave components (including mindfulness) may act by modifying the patient's cognition or beliefs about the severity, frequency, or intolerability of symptoms, thereby improving sleep quality89.

The mediating role of self-control

Consistent with our hypothesis, we found that self-control is another important explanatory mechanism through which mindfulness is linked to sleep quality. First, short-term mindfulness training can significantly enhance an individual's self-control ability90.The theory of limited resources of self-control suggests that individuals possess a finite amount of self-control resources, and the execution of self-control tasks depletes these resources, affecting subsequent self-control activities91. Mindfulness can alleviate self-depletion in self-control92, thus exerting a positive impact on self-control. Second, for individuals with high levels of self-control, when they encounter obstacles or temptations that disrupt sleep, such as the lure of social media, they are capable of organizing and arranging their behavior more effectively to achieve their goals (e.g., obtaining sufficient sleep), thereby enhancing the quality of their sleep60.

The mediating role of bed procrastination

As anticipated, we discovered that bed procrastination mediates between mindfulness and sleep quality, which is consistent with previous research22 and our hypothesis, providing further evidence for the procrastination-health model. This suggests a positive correlation between mindfulness and sleep quality, mediated by the control of risk factors for sleep quality and the reduction of counterproductive protective behaviors. To gain a comprehensive understanding of how mindfulness relates to sleep quality, bed procrastination is a critical component. Mindfulness can help individuals conserve attentional resources by reducing the likelihood of distractions, which in turn can reduce procrastination93. Studies have found that some individuals who procrastinate sleep engage in leisure activities or work before bedtime, and these disturbances may be one of the causes of bed procrastination51, leading to emotional and cognitive arousal; this results in difficulty falling asleep, longer sleep duration, and lower sleep quality94.Conversely, improvements in bed procrastination contribute to the development of healthy sleep habits and improved sleep quality95,96.

The sequentially mediating effects of self-control and bed procrastination

This study provides further support for our hypothesis. Mindfulness was found to have a significant positive correlation with sleep quality, and this relationship was mediated by a sequential mediation process involving self-control and bed procrastination. This result can be explained by the following two reasons. Firstly, higher levels of mindfulness enable people to objectively observe their thoughts and feelings and not act inappropriately in the face of unpleasant thoughts and feelings37.Thus, mindfulness can help individuals improve their self-control97.Secondly, temporal motivation theory asserts that a lack of self-control contributes substantially to delayed susceptibility98 and that individuals with high self-control tend to focus more on long-term goals when making behavioral decisions49 and therefore exhibit less procrastination. Since everyone has a limited amount of time, the longer they procrastinate before bed, the less time they have available for sleep, and circadian sleep patterns are disrupted99, leading to a decrease in sleep quality100.

Limitations and future directions

The sudden stressful event (COVID-19) can cause college students to perceive higher levels of stress, subsequently significantly impacting their sleep quality and mental health. In order to enhance the sleep quality of college students, schools can disseminate knowledge about mindfulness as mindfulness serves as a protective factor for sleep quality. They can also organize regular mindfulness training to increase students’ mindfulness levels to improve sleep quality. Secondly, relevant education departments can develop varied and multi-level self-control courses and programs to improve students’ self-control ability, reduce bed procrastination and improve sleep quality. College students should gradually reduce bed procrastination to improve sleep quality (Supplementary information).

The findings of this study hold significant implications for enhancing the sleep quality of college students. Firstly, educational institutions and relevant departments of the school ought to prioritize addressing sleep-related issues among college students. They can leverage intelligent monitoring methods to identify individuals experiencing sleep problems. Secondly, educational institutions can promote mindfulness knowledge and regularly organize accessible and effective mindfulness training interventions, such as online programs, to enhance students' levels of mindfulness. Additionally, relevant educational authorities can implement diverse and comprehensive self-control courses and programs, targeting various levels of self-control abilities in students. Meanwhile, college students should minimize using electronic devices such as cell phones before bedtime. By doing so, they can effectively mitigate sleep disturbances and actively foster the cultivation of favorable sleep patterns, thus resulting in an overall improvement in sleep quality.

Despite the important findings of this study, there are still some limitations: (1) although this study revealed that mindfulness is related to sleep quality, the causality between variables is not completely reliable because of the limitations of cross-sectional studies; future studies could use longitudinal studies or experimental studies to further verify the results of the study; (2) this study employed a subjective self-reporting method and it should be noted that the mindfulness scale used in this study is single-dimensional rather than multidimensional. Consequently, the results of this study could be validated in the future by adopting other different mindfulness scales. From a broad perspective, it is recommended that future studies integrate behavioural experiments (mindfulness interventions) with self-reported indicators (mindfulness traits) and physiological indicators (e.g., heart rate) in order to enhance the depth and breadth of the findings; (3) this research investigated the mediating mechanism between mindfulness and sleep quality, and future research could investigate certain how negative attention bias59 to explore the relationship between mindfulness and sleep quality; (4) the present study employed a sample comprising Chinese college students rather than clinical samples in the context of a collectivist culture. However, it is recommended to expand the sample diversity to enhance the generalizability of the findings for future investigations; (5) it is acknowledged that the global pandemic caused by the COVID-19 has had a profound impact on the lives of university students, disrupting their learning, social interactions and sleep patterns. Furthermore, the severity of the pandemic and the efficacy of control policies vary considerably from region to region and country to country. This may limit the generalisability of our findings.

Conclusion

Sleep quality is a pressing public concern, and prior research has consistently underscored the significant correlation between mindfulness and sleep quality. However, the precise mechanisms that mediate this relationship have yet to be fully elucidated. In light of this research gap, we conducted a cross-sectional study involving Chinese university students, wherein we identified the mediating influences of self-control and bed procrastination. By investigating these underlying mechanisms, our study contributes to a more comprehensive understanding of the intricate associations between mindfulness and sleep quality. Furthermore, our findings offer valuable insights into practical coping strategies that can be employed to enhance sleep quality among college students.