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. 2023 Sep 1;102(35):e34725. doi: 10.1097/MD.0000000000034725

The effect of short-term cranial electrotherapy stimulation on sleep quality in athletes: A pilot study

Chenhao Tan a, Jinhao Wang a, Jun Yin a, Guohuan Cao a, Jun Qiu a,*
PMCID: PMC10476715  PMID: 37657007

Abstract

Background:

To verify the effect of a 5-day cranial electrotherapy stimulation (CES) intervention on sleep quality in professional athletes.

Methods:

25 professional athletes with poor sleep quality participated in the study. Athletes belonging to the CES group (12 athletes) received a 5-day CES intervention, and those in the control group did not receive any intervention. Objectively and subjected assessed sleep quality was measured 1 week before and after the intervention using an Actigraphy activity recorder, Pittsburgh sleep quality index (PSQI), and Insomnia Severity Index (ISI).

Results:

Objectively measured sleep efficiency increased after CES intervention (P = .013), while the difference between the pretest and posttest of the control group was not significant. For total sleep time (TST), the main effects and interaction were not significant. However, the analysis on wake after sleep onset showed wake after sleep onset decreased after CES intervention (P = .015). No significant interaction was found in subjectively assessed sleep quality but only revealed an improvement in both groups.

Conclusion:

The CES intervention of 30 minutes per day for 5 consecutive days enhanced objective sleep quality in athletes with sleep quality problems. The intervention increased sleep efficiency by lowering awake time after falling asleep.

Keywords: athlete, awake time after falling asleep, cranial electrotherapy simulation, sleep efficiency, sleep quality

1. Introduction

Sleep plays a crucial role in athletes’ recovery from fatigue,[1,2] and extensive research in psychology and physiology has established a strong link between sleep quality and athletic performance.[3,4] Unfortunately, athletes often face a higher risk of experiencing poor sleep quality due to their employment circumstances compared to the general public.[4–6] Consequently, enhancing athletes’ well-being and sports performance by improving sleep quality has become a prominent topic of interest in sports science.

Intervention strategies such as sleep hygiene, assisted sleep, and sleep extension have garnered significant attention from researchers and have demonstrated therapeutic effects.[7,8] For instance, previous studies have highlighted the positive impact of well-designed sleep hygiene leaflets and sleep optimization programs on athletes’ sleep quality and performance.[9,10] Researchers have also explored the effects of interventions such as auditory brainwave entrainment and red light on athletes’ sleep quality and daytime functioning.[11,12] Furthermore, napping and sleep extension have been regularly employed as interventions in athlete sleep research, with more significant improvements observed in sleep quality compared to sleep hygiene education.[13,14] However, a meta-analysis examining the effects of interventions on athlete sleep quality suggested that sleep hygiene and assisted sleep may not significantly improve objective sleep quality, necessitating the development of alternative intervention methods that effectively enhance athlete objective sleep quality while remaining easy to implement.[7]

Cranial electrotherapy stimulation (CES) is a noninvasive sleep intervention technique that gained approval from the US Food and Drug Administration in the 1970s.[15–17] CES originated from “electrosleep,” an electrical stimulation intervention that induces a sleep-like state in participants. By targeting deep brain structures, including subcortical and brainstem regions, CES modulates physiological and biochemical parameters associated with sleep quality, distinguishing itself from conventional interventions like sleep hygiene and assisted sleep.[15,17]

Only a few studies have examined the effects of CES treatment on sleep quality, with most of them focusing on the general population. More evidence should be given regarding the effects of CES interventions, specifically on professional athletes. Athletes possess unique living environments, engage in distinct training activities, and participate in competitive events, which may give rise to sleep problems that differ from those experienced by the general population.[5] Factors such as physical exhaustion, nutrient regulation, and the demands of various sports can contribute to a range of sleep issues unique to athletes.[4]

In response to these athlete-specific characteristics, several researchers have directed their attention toward understanding and addressing the needs of athletes. Sports and medical researchers have started integrating occupational aspects into the screening of sleep quality for athletes.[18] The importance of evaluating the occupational features of athletes has been emphasized in a consensus statement on athlete mental health, which includes sleep disorders.[19] Scales that consider the uniqueness of athletes were established in response to the statement (such as the Athlete Sleep Screen Questionnaire and Athlete Sleep Behavior Questionnaire). The development and application of these scales highlight both the similarities and differences between sleep problems experienced by athletes and the general population. It is recommended that further investigation be conducted to explore the effects of CES on athletes.

While acknowledging that CES may improve sleep quality in athletes, some researchers have examined the benefits of this intervention in student-athletes. For instance, Chang et al (2022) found that a 2-week CES intervention (14 days, 60 minutes per day) reduced the decline in sleep quality experienced by a student-athlete approaching a significant competition.[20] However, it is essential to differentiate between student-athletes and professional athletes, as they vary in academic demands, schedule management, and training routines. Moreover, in the mentioned study, the intervention effect of CES could potentially be confounded by competition-induced anxiety, apart from the occupational difference. Therefore, further research is needed to establish the impact of CES on the sleep quality of professional athletes while accounting for the influence of competition.

Additionally, when applying CES to professional athletes, the intervention time efficiency should be considered. Previous research has shown that a 60-minute intervention can affect brain electrical activity, and a 5-day intervention can improve sleep outcomes in student-athletes compared to a fourteen-day intervention.[20–22] Building upon these findings, our study aims to investigate the effect of a shorter CES intervention duration on the sleep quality of professional athletes.

In summary, the objective of the current study was to examine the effects of CES intervention on subjectively and objectively measured sleep quality in professional athletes. Furthermore, we conducted a 5-day intervention period to explore the potential improvement in sleep quality among professional athletes with a shorter intervention duration.

2. Materials and Methods

2.1. Participants

Participants were recruited from Shanghai modern pentathlon team, Shanghai fencing team, Shanghai basketball team, Shanghai badminton team, Shanghai table tennis team, Shanghai handball team, Shanghai boxing team, Shanghai judo team, Shanghai karate team, and Shanghai Chinese martial arts team. Based on a survey that covered 205 professional athletes from mentioned teams, 31 professional athletes with problems in sleep quality participated in the current study. Fifteen athletes were sent to the CES group, and 16 were sent to the control group.

Because of vacation, competition, injury, or failure to complete the intervention or test as needed, 3 of the CES intervention group and 3 of the control group were eliminated from the analysis. 25 athletes completed the study (10 females; average age = 21.88, SD = 3.24; 12 belongs to the CES intervention group; Fig. 1). According to the design and previous studies, the minimum sample size was calculated to be 22, based on an effect size of 0.30, an α-level of 0.05, and a power of 0.90. All participants gave their informed consent for inclusion before participating in the study. The study was conducted in accordance with the Declaration of Helsinki, and the protocol was approved by the Ethics Committee of the Shanghai Research Institute of Sports Science (Shanghai Anti-Doping Agency).

Figure 1.

Figure 1.

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Flow diagram of subjects in the trial.

2.2. Randomization and masking

The assignment of individuals to subgroups was based on random sampling. Subjects were given their ID when they took the pretest. These IDs were subsequently reordered using computer-generated random numbers. The first half of the reordered IDs were used as the experimental group and the second half as the control group.

2.3. Design

We conducted a 2 (Intervention type: CES intervention, control) × 2 (Time: pre-intervention, post-intervention) mixed design. Intervention type was a between-subject variable. Subjectively measured sleep quality and objectively measured sleep quality were dependent variables.

2.4. Subjectively measured sleep quality

The Pittsburgh Sleep Quality Index (PSQI) and the Insomnia Severity Index (ISI) were used to subjectively assess sleep quality.

PSQI is a 19-item self-report scale that evaluates 7 aspects of sleep. Sleep quality is represented by the PSQI global score. The higher the score, the worse the sleep quality. A score of more than 5 indicates poor sleep quality.[23]

ISI is a self-report scale comprised of 7 items evaluating the nature, severity, and impact of insomnia. A higher total score indicates more severe sleep difficulties.[24] Adequate psychometric properties for both PSQI and ISI have been reported in previous studies.[25] In this study, participants were instructed to respond based on their recent experiences.

2.5. Objectively measured sleep quality

Wristwatch Actigraph recorders were used to measure objective sleep quality before and after the CES intervention (Actigraph wGT3X-BT; ActiGraph, LLC). The wristwatch was worn on the participant non-dominant wrist at night for 3 days, 1 week before and after the intervention, to capture movement during sleep. The online sample rate was 100Hz, and the data was offline resampled into 60-second epochs. Sleep time and awake time were recorded by participants. ActiLife v6.13.4 was used to analyze the sleep metrics (i.e., total sleep time - TST, wakefulness after sleep onset - WASO, and sleep efficiency).

The wristwatch of Actigraph is a reliable method to measure the sleep quality of athletes, and its results are highly correlated with those of polysomnography.[26–28]

2.6. CES intervention

HS-100H CES device (Chongqing Haikun Medical Instruments Co., Ltd., China) was used to exert CES intervention. The largest frequency in the current study intervention mode was 1.3kHz, the pulse width was 90s, the peak current was <10mA, and the stimulate current included nonpolar exponential wave and rectangular wave. Electrodes attached to the bilateral mastoid provided treatment. The stimulus intensity is divided into 32 levels. The level of the intervention was determined by the participant absolute sensory threshold. The duration of intervention can be set between 1 to 60 minutes. In the current study, the duration was fixed at 30 minutes.

2.7. Procedure

The study was conducted in 4 phases, all of which took place in the dormitories and psychological laboratory at the athletes’ training base. In the first phase, a sleep quality survey was administered to ten sports teams with the support of coaches. Athletes who scored higher than 5 on the PSQI were invited to participate in a brief interview. Those experiencing special events that could temporarily affect sleep quality (e.g., injury, competition anxiety, sharing a room with a snorer) were excluded from the study based on the interview. Subsequently, athletes who obtained their coach agreement were included. Participants were then randomly assigned to either the CES intervention or control groups.

The second phase involved a pretest conducted 1 week before the intervention. During this week, participants individually completed the PSQI and ISI scales. From Tuesday to Thursday, participants wore the Actigraph wGT3X-BT device at night and recorded the time they decided to go to sleep (rather than lying in bed) and the time they woke up (rather than getting out of bed) under the experimenter guidance.

The third phase encompassed the intervention itself. Participants assigned to the CES intervention group received a 30-minute CES intervention every evening from Monday through Friday (18:30 to 20:30). In each intervention session, an experimenter first assisted the participant in cleaning the skin around the mastoids. Subsequently, 2 single-use electrodes were adhered to the mastoids and connected to the HS-100H device via cables. The experimenter then initiated a 30-minute program and gradually increased the stimulation intensity until the participant reported feeling a mild stimulus. At the end of the intervention, the experimenter assisted the participant in removing the electrodes. If the individual reported any adverse sensations, the program was immediately stopped. Only participants assigned to the CES intervention group received this treatment, while those in the control group did not receive any intervention.

The fourth and final phase was the posttest, conducted 1 week after the 5-day intervention. During this week, participants independently completed the PSQI and ISI scales. Participants also wore the Actigraph wGT3X-BT device at night from Tuesday to Thursday. They recorded the time they decided to go to sleep (rather than lying in bed) and the time they woke up (rather than getting out of bed) under the experimenter instructions.

2.8. Statistical analysis

SPSS (version 20; SPSS Inc., Chicago, IL) was used to analyze all data. Descriptive values are given as means and standard deviations. According to the 2 (Intervention type: CES intervention, control) × 2 (Time: pre-intervention, post-intervention) mixed design, we conducted 2 × 2 mixed Analyses of variance (ANOVA) with Intervention type as the between-subject variable and Time as the within-subject variable (repeated measured). The effect size was calculated by using partial eta squared (ηp2).

3. Results

3.1. Subjectively measured sleep quality

The analysis on PSQI revealed a main effect of Time, F(1, 23) = 9.440, P = .005, ηp2 = .291. To be specific, the score of the posttest (M = 7.120, SD = 1.986) was lower than that of the pretest (M = 8.680, SD = 2.393). The main effect of Intervention type was not significant, F(1, 23) = 2.387, P = .136, ηp2 = .094. The interaction between 2 independent variables was not significant, F(1, 23) = 0.957, P = .338, ηp2 = .040.

In the ISI, we also found a significant main effect of Time, F(1, 23) = 6.339, P = .019, ηp2 = .216. The ISI of posttest (M = 8.680, SD = 5.014) was lower than that of pretest (M = 10.280, SD = 3.422). However, the main effect of Intervention type was not significant, F(1, 23) = 2.481, P = .129, ηp2 = .097. The interaction between 2 independent variables was not significant, F(1, 23) = 0.359, P = .555, ηp2 = .015.

3.2. Objectively measured sleep quality

The analysis of sleep efficiency revealed a significant interaction between Intervention type and Time, F(1, 23) = 6.107, P = .021, ηp2 = .210. Simple effect analysis showed that for the CES intervention group, sleep efficiency tested after the intervention was higher than pretest, P = .013; whereas for the control group, the difference between pretest and posttest was not significant, P = .460 (Table 1, Fig. 2). However, the main effect of Intervention type was not significant, F(1, 23) = 3.744, P = .065, ηp2 = .140 The main effect of Time was not significant, F(1, 23) = 2.048, P = .166, ηp2 = .082.

Table 1.

Descriptive results of sleep quality (M ± SD).

CES Control
Pretest Posttest Pretest Posttest
PSQI 9.500 ± 2.939 7.417 ± 1.730 7.923 ± 1.498 6.846 ± 2.230
ISI 11.750 ± 3.019 9.750 ± 4.224 8.923 ± 3.303 7.692 ± 5.633
Sleep efficiency 0.883 ± 0.043 0.910 ± 0.032 0.867 ± 0.051 0.860 ± 0.053
TST (Min.) 405.556 ± 51.234 404.333 ± 64.579 398.205 ± 35.312 408.654 ± 34.452
WASO (Min.) 49.361 ± 17.000 36.806 ± 11.254 58.667 ± 25.438 62.744 ± 25.273
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CES = cranial electrotherapy stimulation, ISI = insomnia severity index, PSQI = Pittsburgh sleep quality index, TST = total sleep time, WASO = wakefulness after sleep onset.

Figure 2.

Figure 2.

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Changes in sleep efficiency in 2 groups (*P < .05, **P < .01).

The analysis on TST did not reveal any main effect or interaction. Specifically, the main effect of Intervention type was not significant, F(1, 23) = 0.007, P = .934, ηp2 < .001. The main effect of Time was not significant, F(1, 23) = 0.549, P = .466, ηp2 = .023. The interaction between 2 independent variables was not significant, F(1, 23) = 0.879, P = .358, ηp2 = .037.

The analysis on WASO revealed a significant interaction, F(1, 23) = 6.368, P = .019, ηp2 = .217. Simple effect analysis showed that for the CES intervention group, WASO tested after the intervention was shorter than the pretest, P = .015, whereas for the control group, the difference between the pretest and posttest was not significant, P = .381 (Table 1, Fig. 3). The main effect of Intervention type was significant, F(1, 23) = 5.279, P = .031, ηp2 = .187. The WASO of the CES group (M = 45.844, SD = 20.744) was shorter than that of the Control group (M = 61.850, SD = 22.216). The main effect of Time was not significant, F(1, 23) = 1.655, P = .211, ηp2 = .067.

Figure 3.

Figure 3.

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Changes in TST and WASO in 2 groups (*P < .05, **P < .01). TST = total sleep time, WASO = wakefulness after sleep onset.

4. Discussion

Sleep quality significantly impacts athletic performance, with numerous studies highlighting its crucial role in maintaining peak performance among athletes. However, professional athletes face challenges that increase their risk of experiencing sleep quality difficulties, such as demanding schedules, organizational management, and training loads. Given this context, there is a growing demand for effective intervention strategies tailored to the needs of professional athletes.

In this study, we aimed to investigate the effects of a 5-day CES intervention on the sleep quality of professional athletes. The results revealed that while the CES intervention did not impact subjectively assessed sleep quality significantly, it did improve objectively measured sleep quality. Specifically, the CES intervention and control groups notably decreased the ISI as a subjective measure. Regarding objective measures, the CES intervention significantly enhanced sleep efficiency, primarily attributed to a reduction in Wake After Sleep Onset (WASO) rather than a lengthening of TST.

The FDA approved CES as a noninvasive neuromodulation technique to enhance sleep quality almost 50 years ago. However, the literature on the effect of CES on sleep quality in the general population has yielded inconsistent findings. Moreover, a recent review highlighted that a few studies failed to observe the anticipated intervention effect, albeit relatively uncommon.[29] These findings raise questions regarding the suitability of CES as a sleep quality intervention strategy for athletes.

Given the need for further research to substantiate the benefits of CES interventions for sleep quality in professional athletes, it is worth noting that only 1 study has explored the effects of interventions on student athletes.[20] In this study, researchers provided a 14-day intervention to student-athletes before engaging in significant competitions over 2 months. Interestingly, the CES and shame therapy conditions resulted in a decline in objectively observed sleep efficiency following the intervention. Subsequent analysis revealed that the CES intervention only led to a slower decrease in sleep efficiency. However, these initial findings do not provide definitive evidence for the effect of CES. In contrast, our study demonstrated significant improvements in objectively evaluated sleep quality among elite athletes, which diverges from previous findings.

Although the precise mechanism of CES intervention remains unclear, several imaging studies have suggested that CES affects various cortical and subcortical structures, including the thalamus, leading to neurochemical changes, deactivation of specific cortical areas, and modulation of brain rhythms. These effects may contribute to improvements in sleep function.[29] Based on this potential mechanism, the disparity between our study results and previous findings can be attributed primarily to the influence of pre-competition pressure. Specifically, Chang and colleagues administered CES to student-athletes approaching competitions within 2 months.[20] This recruitment criterion implied that the competition was imminent throughout the intervention period, potentially resulting in heightened competition anxiety and diminishing the efficacy of CES.[30,31]

Student-athletes represent a unique population as they possess dual identities as students and athletes.[32] Consequently, their sleep issues are specific to their occupational context. Academic pressures, school schedules, and limited training time due to the trade-off between training and academics can all attenuate the impact of interventions. In contrast, the professional athletes in our study prioritize training as a central aspect of their daily routine. This leads us to infer that the observed phenomenon of CES primarily reducing WASO without extending TST may be due to professional sports teams’ tight control of schedules. Therefore, the absence of pre-competition pressure and the distinct occupational features of professional athletes in our study ensured the effectiveness of CES intervention.

Regarding the subjectively assessed sleep quality outcomes, our findings do not contribute significantly to the ongoing debate on this topic. Previous research demonstrated the beneficial effects of CES on chronic insomnia patients using the PSQI and ISI scales.[33] However, in our study, improvements were observed in both groups. The inability to detect the effectiveness of CES may be attributed to the limitations of the scales used. These limitations stem from 2 factors: the clinical application of the scales and the target population. Since sleep quality was subjectively assessed using self-report scales primarily intended for clinical use, these scales may not accurately capture the impact of CES on athletes whose symptoms had not reached a certain level of severity. Furthermore, when assessing the athletic population, the commonly used scales for measuring sleep problems in the general population may lack specificity.[5,18] Despite researchers’ concerns regarding scale limitations and the development of sleep screening scales specifically for athletes,[18] the precision of these screening tools remained insufficient for our study. Moreover, at the posttest stage, both subjective measures showed a significant decrease in scale scores. This finding can be attributed to demand characteristics or expectation bias. Considering the focus of our study on athletes with sleep quality issues and its intervention-oriented nature, it is plausible that the bias was induced by either the informed consent process or the participants’ personal expectations of improvement. The partial support for this hypothesis comes from the absence of similar changes in the objective measures. Therefore, this phenomenon serves as a timely reminder of the limitations inherent in relying solely on subjective measurement tools.

While the mechanism of CES remains unclear, and the results of subjective measures may not be optimal, this study demonstrated the enhancing effect of CES on sleep efficiency in athletes. Previous research on improving sleep quality in athletes has primarily focused on sleep hygiene education, assisted sleep techniques, sleep recovery, and strategies to lengthen sleep duration. However, these approaches have yet to yield robust improvements in objectively measured sleep quality.[7] Compared to these methods, CES not only improves athletes’ objective sleep quality but also imposes fewer professional demands and subjective motivational requirements on athletes. Additionally, CES has a lesser impact on training, recovery, and treatment schedules, making it an ideal intervention for use in sports teams.[34] Furthermore, the current study employed a more time-efficient intervention protocol, reducing the intervention period to 5 days with 30 minutes of intervention per day. Overall, CES has the potential to increase athletes’ sleep efficiency in terms of objective sleep quality and has shown preliminary benefits in the professional athlete population, thereby introducing new possibilities for improving athletes’ sleep outcomes.

While this study provides preliminary evidence regarding the effect of CES on improving sleep quality in athletes, 2 limitations should be acknowledged. Firstly, the sample was limited due to the access criteria and intervention period. This study focused specifically on professional athletes experiencing sleep quality issues. It is important to note that professional athletes represent a small fraction of the overall population. The combination of excluding the competition period, requiring specific scale scores to establish the presence of sleep problems, and ensuring the intact and timely implementation of the intervention within the sports team schedule significantly reduced the available sample size, which was already limited. The second limitation pertains to the subjective assessment of sleep quality solely through self-assessment scales, without considering daytime tasks.[34] This makes it challenging to establish a direct link between improved sleep quality and enhanced exercise performance. Therefore, future studies should address 2 key areas of improvement. First, further studies should investigate the impact of CES interventions on various sleep quality issues in a broader population of elite athletes. Second, further studies should combine sports science research with questionnaires and behavioral experiments relevant to sports performance to assess subjective sleep quality.

5. Conclusions

The CES intervention of 30 minutes per day for 5 consecutive days enhanced objective sleep quality in athletes with sleep quality problems. The intervention increased sleep efficiency by lowering awake time after falling asleep. However, the electrical stimulation intervention cannot affect the athletes’ subjectively measured sleep quality.

Acknowledgments

The authors would like to thank all subjects for volunteering their time for this study.

Author contributions

Conceptualization: Chenhao Tan, Jinhao Wang, Jun Qiu.

Data curation: Chenhao Tan, Jinhao Wang, Jun Yin.

Formal analysis: Chenhao Tan.

Funding acquisition: Jun Qiu.

Investigation: Chenhao Tan, Guohuan Cao.

Methodology: Chenhao Tan, Jun Yin, Guohuan Cao.

Project administration: Chenhao Tan, Jun Qiu.

Resources: Jinhao Wang.

Supervision: Jun Qiu.

Validation: Chenhao Tan.

Writing – original draft: Chenhao Tan.

Writing – review & editing: Chenhao Tan, Jinhao Wang.

Footnotes

CT and JW contributed equally to this work.

The authors have no conflicts of interest to disclose.

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

This research was supported by the Shanghai “Science and Technology Innovation Action Plan” social development science and technology research projects (22dz1204601) by the Science and Technology Commission of Shanghai Municipality. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

How to cite this article: Tan C, Wang J, Yin J, Cao G, Qiu J. The effect of short-term cranial electrotherapy stimulation on sleep quality in athletes: A pilot study. Medicine 2023;102:35(e34725).

Contributor Information

Chenhao Tan, Email: tanchenhao92@163.com.

Jinhao Wang, Email: wangjinhao28@163.com.

Jun Yin, Email: qiujun@shriss.cn.

Guohuan Cao, Email: caoguohuan@shriss.cn.

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