Article Text
PDF
Abstract
Objective Mindfulness-based stress reduction (MBSR) is a meditation-based therapy originally recommended for stress management. However, it is currently used to alleviate sleep disturbances. Therefore, this contemporary systematic review aimed to elucidate the clinical effects of MBSR on sleep quality and sleep-related daytime impairment in adults with sleep disturbances, including chronic insomnia disorders.
Design Systematic review and meta-analysis of randomised controlled trials (RCTs).
Methods A comprehensive search was conducted using the following databases: Ovid MEDLINE, AMED, Ovidembase, PsycINFO, Cochrane Library, CINAHL, and four domestic databases: KoreaMed, KISS, KMbase and NDSL. The final search update was performed in June 2022. Two researchers independently selected relevant studies, assessed the risk of bias and extracted the data.
Results Of the 7516 records searched, 20 RCTs and 21 reports were included. In the subgroup analysis, MBSR did not improve objective or subjective sleep quality in chronic insomnia and cancers. However, MBSR versus waitlist control might have been effective in improving subjective sleep quality, but with substantial heterogeneity (standardised mean difference=−0.32; 95% CI: −0.56 to –0.08; I2=71%). In addition, MBSR compared with active control did not improve the sleep-related daytime impairments including depression, anxiety, stress, fatigue and quality of life. The overall risk of bias included in this review was a concern because of performance and detection bias.
Conclusions MBSR might be ineffective for improving sleep quality in patients with chronic insomnia and cancers. In addition, more than half of the RCTs included in this review had small sample sizes and were vulnerable to performance and detection biases. Therefore, well-designed RCTs with larger sample sizes are required to confirm the clinical effects of MBSR in adults with sleep disturbances.
PROSPERO registration number CRD42015027963.
- sleep medicine
- complementary medicine
- primary care
Data availability statement
Data are available upon reasonable request. Our study uses published data only. The original contributions presented in the study are included in the article and online supplemental material, further inquiries can be directed to the corresponding author.
This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.
Statistics from Altmetric.com
STRENGTHS AND LIMITATIONS OF THIS STUDY
The present study is a contemporary systematic review and meta-analysis of the effectiveness of mindfulness-based stress reduction interventions for improving sleep quality and sleep-related daytime impairments in people with sleep disturbance.
This systematic review and meta-analysis included subgroup analyses and comparisons according to the various types of participants in an effort to provide concrete evidence on the effectiveness of interventions.
Objective assessment of sleep quality including subjective sleep quality measures was a key feature of the analysis.
The overall risk of bias among the studies included in the present systematic review raises concerns, making definitive conclusions difficult.
Introduction
Sleep disturbances are a common health problem affecting approximately 20%–30% of adults,1 and include difficulties in falling asleep, maintaining normal sleep or sleeping for sufficient duration.2 Individuals are diagnosed with sleep disturbances if the symptoms seriously affect their social and professional performance.3 According to American guidelines on chronic insomnia treatment published in 2017,4 pharmacotherapy and non-pharmacological therapy are the two major treatment modalities for sleep disturbances. Although pharmacotherapy is more effective than non-pharmacological therapy, it can have various side effects such as substance abuse induced by physical/psychological tolerance, withdrawal, drug–drug interactions, abnormal thoughts, behavioural changes and headaches.5 6 Recently, patients with sleep disturbances have shown a preference for non-pharmacological therapy.7
Mindfulness-based stress reduction (MBSR) is a key non-pharmacological type of mindfulness-based intervention (MBI) that effectively relieves insomnia by decentring.8 The MBSR method developed by Jon Kabat-Zinn in 1979 is a modern adaptation of mindfulness meditation practised in ancient Buddhism.9 Mindfulness refers to the way of life or state of mind, in which individuals are aware of their thoughts, emotions and experiences at a given moment.9 It focuses on regulating the levels of physical and psychological stresses, including those caused by cancer, chronic pain and sleep disturbance.9 Physiological changes during meditation activate the parasympathetic-limbic pathway, which reduces the heart rate, systolic blood pressure, respiratory rate, and consequently, stress.10 Stress is the primary cause of sleep disturbances.11 Thus, stress reduction may improve sleep quality or duration.
Although several systematic reviews and meta-analyses have investigated the effects of MBSR on sleep disturbances, non-comparative and comparative studies were simultaneously included in previous reviews,12 13 and some failed to examine the effectiveness of MBSR due to co-interventions.14–16 Moreover, several reviews only included patients with insomnia and not those with sleep disturbances.16 17 The 2021 American Academy of Sleep Medicine clinical practice guidelines18 contain no recommendation for mindfulness therapies for chronic insomnia disorder. Therefore, this contemporary systematic review aimed to elucidate the clinical effects of MBSR on sleep quality and sleep-related daytime impairment in individuals with sleep disturbances, including chronic insomnia disorders.
Methods
Search strategy and eligibility criteria
The following databases were searched for relevant studies: Ovid MEDLINE, AMED, Ovidembase, PsycINFO, the Cochrane Library, CINAHL, KoreaMed, Korean Studies Information Service System, Korean Medical Database and National Digital Science Library. Additional searches were performed by reviewing the references provided in the relevant studies.
Search terms were established by combining “sleep disturbance” and “mindfulness”. In international databases where Medical Subject Headings were available, terms related to sleep disturbance and mindfulness (using exp Sleep disturbances/AND exp Meditation/) were used with keywords. In other databases where controlled vocabulary were unavailable, keywords or text words were used. Proximity operators, Boolean operators and truncation searches were used to comprehensively search the literature (online supplemental appendix 1). A literature search was conducted in October 2018, and the final search update was performed in June 2022.
Supplemental material
Inclusion and exclusion criteria
The main study question and inclusion criteria were as follows:
Population
Adults aged ≥18 years who experienced sleep problems or disturbances including insomnia.
Intervention
Participants performed simple and formal meditation such as body-scan meditation (including stretching and postural adjustment), seated meditation, walking meditation and Hatha yoga. The studies included in this analysis examined the administration of a structured mindfulness-based programme to participants with sleep disturbance for a minimum of 6 weeks.
Comparison
Passive control including waitlist, and active control groups, such as those receiving usual care, cognitive–behavioural therapy and sleep-hygiene education.
Outcomes
The primary outcomes were: objective sleep quality measured with wrist actigraphy, and subjective sleep quality assessed using self-reported questionnaires. The secondary outcomes were changes in sleep-related daytime impairments such as depressive symptoms, anxiety, stress, fatigue and reduced quality of life.
Study design: randomised controlled trial
Studies were excluded if: (1) participants worked in shifts or were jet-lagged after a trip; (2) it was not possible to determine the effect size of MBSR alone due to complex interventions; and (3) they were published as abstracts, dissertations or reports.
Two researchers independently selected studies based on the inclusion and exclusion criteria. The titles and abstracts were reviewed during the first screening, and the full texts were reviewed during the second screening. In cases of disagreement between the two researchers on the final selection of studies, consensus was reached by involving a third researcher.
Assessment of the risk of bias
The Cochrane risk of bias tool was used by two researchers who independently assessed the risk of bias in the included studies.19 The researchers rated the risk of bias for each domain as ‘low’, ‘high’ or ‘unclear’. In cases of disagreement between the two researchers, a consensus was reached by involving a third reviewer.
Data extraction
The study characteristics, intervention information and outcome measures for the assessment of clinical effects were extracted from the selected studies using a predefined data extraction form. Two researchers independently collated the data, and all discrepancies were resolved through a consensus with a third researcher. If insufficient data were reported, a request for additional data was sent to the corresponding author via email.
Statistical analysis
A meta-analysis was performed using a random-effects model considering the heterogeneity of the included studies. Review Manager software (RevMan V.5.3.5, Copenhagen, Denmark, 2011) was used for data analyses. For studies measuring outcomes at multiple follow-ups, the final value measured at the end of the follow-up was chosen. Continuous outcome data were pooled using a weighted mean difference if the same measurement tools were used, and a standardised mean difference (SMD) if different measurement tools were used.
Because the health conditions of adults with sleep disturbance and existing treatments were expected to be diverse, a subgroup analysis was performed according to type of participants and controls.20 Heterogeneity was assessed using I2 and Q statistics. An I2 >50% indicated significant heterogeneity.21 Publication bias was examined using a funnel plot if a meta-analysis included more than 10 studies.22 If a study reported incomplete outcome data and the authors could not manage the missing data using the formulas presented by Hozo et al,23 a narrative description was used to summarise the results.
Patient and public involvement
There was no direct patient or public involvement in this review.
Results
Study selection and study characteristics
In total, 7516 records were retrieved from multiple databases. After removing duplicates with EndNote, 6534 records were screened. Of these, 86 reports were selected by two independent researchers after the first screening. In the second round, the full texts of these articles were reviewed. Consequently, 65 reports were excluded based on the exclusion criteria (figure 1 and online supplemental appendix 2). Ultimately, 20 studies from 21 reports were included in this review.
Study selection process.
The general characteristics of the included studies are shown in table 1. Eleven waitlist control groups were included, all of which were waitlisted controls. The remainder were active control groups comprising those receiving usual care, positive adult development, behavioural therapy for insomnia and so on.
Characteristics of included studies
Of the 20 studies included, 8 (40%) involved patients with cancer and 3 (15%) involved patients with chronic mental disorders (chronic insomnia). MBSR was provided for 8 weeks in 14 (70%) studies. In nine studies (45%), interventions were performed for 2 hours per week. The time spent by individuals performing home exercises ranged from 15 to 45 min in 16 (80%) studies. Most studies did not report whether participants were prescribed sleep medications.
Risk of bias assessment
A summary of the risk of bias in the included studies is presented in figure 2. Under the domain of generating a random allocation sequence, 18 (90%) studies were rated as having a low risk of bias as they specifically described the appropriate random sequence generation methods. Eight studies (40%) were rated as having an unclear risk of bias, because they did not mention the allocation concealment process. Regarding the blinding of participants and personnel, three (15%) studies in which investigators or participants were blinded and did not affect the outcomes were evaluated as having a low risk of bias. Three (15%) studies were rated as having a low risk of detection bias because the outcome assessors were blinded. The risk of bias associated with reporting incomplete outcomes was deemed to be low in 11 (55%) studies, because an intention-to-treat analysis was performed and the dropout rate was similar between groups. Four (20%) studies were evaluated as having an unclear risk of bias for selective outcome reporting, as they only reported on the value of change. Therefore, the overall risk of bias across studies was a concern, although blinding of participants and personnel was difficult during the intervention trial.
Risk of bias assessment. (A) Risk of bias graph: review authors’ judgements about each risk of bias item presented as percentages across all included studies. (B) Risk of bias summary: review authors’ judgements about each risk of bias item for each included study.
Effects of MBSR
Primary outcomes: sleep quality
Objective sleep quality
Four studies reporting objective sleep quality by using sleep efficiency (SE) with wrist actigraphy were included in the meta-analysis. SE is considered the standard for evaluating the efficacy of insomnia interventions,24 with a high SE score indicating long sleep duration. When compared with the controls, MBSR did not improve SE (MD=−1.17; 95% CI: −4.26 to 1.92).25–28 Due to significant heterogeneity (I2=68%), we performed MBSR subgroup analyses according to the types of participants and type of controls. The analyses revealed that when compared with the control group, MBSR did not increase SE (table 2 and online supplemental appendix 3).
Subgroup analysis of MBSR versus controls in sleep quality for people with sleep disturbance
Patient-reported sleep quality
In 17 studies, 2127 participants were included to examine the pooling effects of sleep quality by using patient-reported questionnaires. The SMD of MBSR versus controls was −0.17 (95% CI: −0.35 to 0.01; I2=74%). As the heterogeneity of the pooled estimate was substantial, subgroup analyses were conducted. Among the participants, groups including other conditions (solid organ transplant, patients with fibromyalgia, menopausal-transition women, etc) showed an improvement in sleep quality (SMD=−0.21; 95% CI: −0.36 to –0.06; I2=36%).29–35 Moreover, MBSR might have demonstrated significantly improved sleep quality versus the waitlist control group. However, it should be noted that the heterogeneity was significant (SMD=−0.32; 95% CI: −0.56 to –0.08; I2=71%) (table 2 and online supplemental appendix 4).27 30–33 36–39 No obvious publication bias was detected using the funnel plot (figure 3).
Funnel plot of MBSR versus controls; outcome measure: patient-reported sleep quality. MBSR, mindfulness-based stress reduction; SMD, standardised mean difference.
Similar to the results of meta-analyses, the results of three studies not included in the meta-analysis were as follows: MBSR compared with active control did not improve sleep quality in patients with breast cancer (between group p=not significant),40 and in mothers of children with autism and other disabilities (Effect size=0.03, SE=0.02, p=not significant).41 MBSR versus waitlist control improved sleep quality in failed back surgery syndrome in long-term follow-up (MD=1.9, SD=3.3, p<0.047).42
Secondary outcomes: sleep-related daytime impairments
Depressive symptoms
Ten studies including 499 participants who received MBSR and 560 controls were included in the meta-analysis. MBSR reduced depressive symptoms, compared with the controls but with considerable heterogeneity (SMD=−0.35; 95% CI: −0.68 to –0.02; I2=83%). Therefore, we conducted subgroup analyses to explore the causes of heterogeneity. In the subgroup analysis according to the type of participants, MBSR did not improve depressive symptoms (table 3). However, MBSR versus active control slightly improved depression level in mothers of children with autism spectrum disorder and other disabilities (ES=0.04, SE=0.02, p<0.05).41
Subgroup analysis of MBSR versus controls in sleep-related daytime impairments
Anxiety
The effect of MBSR on anxiety was investigated in nine studies, including 935 participants. The results showed that MBSR reduced anxiety levels compared with that in the controls, but with substantial heterogeneity (SMD=−0.41; 95% CI: −0.72 to –0.09; I2=79%). Therefore, we performed subgroup analyses to address the heterogeneity (p<0.0001). In the subgroup analysis according to type of controls, MBSR compared with waitlist control might be effective in reducing anxiety, but with significant heterogeneity (SMD=−0.75; 95% CI: −1.44 to –0.07, I2=90%, p<0.00001) (table 3).33 36 38 39 However, MBSR versus active control did not decrease anxiety level in mothers of children with autism spectrum disorder and other disabilities (ES=0.01, SE=0.02, p=not significant).41
Stress
Six studies (n=824) were included in this meta-analysis.25 31 33 37 38 43 When compared with the controls, MBSR had no effect on stress (SMD=−0.32; 95% CI: −0.70 to 0.06; I2=85%). We then performed subgroup analyses to address the considerable heterogeneity and found that according to the type of participants, MBSR did not improve stress levels when compared with the control group (table 3). Consistently, MBSR versus active control did not decrease parental distress level in mothers of children with autism spectrum disorder and other disabilities ((ES=0.00, SE=0.02, p=not significant).41
Fatigue
Seven studies, including 372 participants who underwent MBSR, and 378 controls were included in the meta-analysis.31 36–38 43–45 MBSR did not decrease fatigue level, compared with controls (SMD=−0.23; 95% CI: −0.51 to 0.04; I2=66%). To address the substantial heterogeneity, subgroup analyses according to the type of participants and type of controls were performed. Consistently, MBSR did not improve stress, when compared with the controls (table 3).
Discussion
This systematic review and meta-analysis revealed that MBSR had no effect on the improvement of sleep quality in chronic insomnia and patients with cancer. However, when compared with waitlist controls, MBSR might be an effective treatment for improving subjective sleep quality as measured by self-report questionnaires. However, we observed considerable heterogeneity in the subgroup analysis. This discrepant result can be explained by the placebo effect in the open-label trial investigating the effect of MBSR compared with waitlist controls.46 Furthermore, the most studies included in this meta-analysis raised concerns regarding the detection bias, despite accounting for the difficulty of blinding in behavioural intervention trials.
In a meta-analysis and subgroup analysis, MBSR measured using wrist actigraphy did not improve objective sleep quality versus the controls. These findings were consistent with those of a study that used an activity tracker as an objective outcome measure to examine the effect of MBIs on sleep disturbances.13 Furthermore, Wang et al16 reported that MBSR did not improve sleep duration when measured by wrist actigraphy. In a study by Gong et al,14 MBIs improved self-reported sleep quality, but had little effect on sleep duration. Similarly, whereas MBIs effectively reduced self-reported insomnia, they had little effect on objective sleep data obtained using polysomnography and wrist actigraphy.47
In this review, exposure to MBSR interventions in participants categorised by other conditions (solid organ transplant, patients with fibromyalgia, menopausal-transition women, etc) improved the self-reported sleep quality with a small effect size. However, caution is required because of the clinical heterogeneity of the studies included in this subgroup. Therefore, the results should be carefully interpreted until further trials confirm or refute them, especially since the results of this study in favour of intervention might be associated with raised expectations in intervention groups with unblinded or inadequate blinding.48
In a previous systematic review, MBI of healthy adults with insomnia49 or sleep disorders, and patients diagnosed with insomnia16 reported improved subjective sleep quality as measured by a self-reported questionnaire. However, in this review, the MBSR programme did not improve subjective sleep quality when measured using a self-reported questionnaire for chronic insomnia and cancer. In fact, no recommendations exist for mindfulness therapies for chronic insomnia in recently published clinical practice, which may support the findings of this study.18 However, in the case of patients with cancer with sleep disturbance, additional evidence is required as the data are insufficient to evaluate the effect.18
In the overall meta-analysis, MBSR effectively reduced depressive symptoms and anxiety when compared with the control group. However, the results should be interpreted with caution because of the substantial heterogeneity. The results may be explained by the inclusion of participants with clinical conditions in the meta-analysis. In the subsequent subgroup analysis, MBSR did not improve depressive symptoms and anxiety levels when compared with controls. Similarly, in a meta-analysis by Haller et al, MBSR did not decrease anxiety levels in patients with breast cancer at long-term follow-up (anxiety k=2, SMD=−0.22, 95% CI: −0.48 to 0.05).50 Moreover, a systematic review of mindfulness-based and acceptance-based interventions in patients with fibromyalgia51 found no difference between groups in the anxiety levels and depression symptoms measured at follow-up. However, these results were inconsistent with those of a 2019 study by Haugmark et al51 showing that mindfulness and acceptance-based interventions effectively reduced depression in patients with fibromyalgia. An explanation for this finding may be that Haugmark et al51 examined the effects of mindfulness meditation plus Qigong movement therapy, acceptance and commitment therapy, and mindfulness-based cognitive therapies, in addition to MBSR.
The subgroup analyses reported in this study revealed that MBSR did not improve stress, fatigue and quality of life in people with sleep disturbances. In a systematic review of the stress-reducing effect of MBI in patients with breast cancer, MBSR compared with usual care did not effectively reduce stress and fatigue in the medium term (SMD=−0.25, 95% CI: −0.68 to 0.19 for stress level; SMD=0.19; 95% CI: −0.50 to 0.88 for fatigue level).50 These results were consistent with those of meta-analyses that used outcome measures assessed at the end of follow-up.
In this review, both randomised controlled trials (RCTs) evaluating the effect of MBSR on menopausal women and patients with solid organ transplants reported no effective improvement in quality of life.30 34 These results were consistent with those of the systematic review on mindfulness-based and acceptance-based interventions in patients with fibromyalgia,51 which reported no significant differences between intervention and control groups in health-related quality of life measured post-intervention and at follow-up (SMD=−0.74, 95% CI: −2.02 to 0.54; and SMD=−0.61, 95% CI: −1.48 to 0.26, respectively). Additionally, a meta-analysis of the effects of MBSR in patients with breast cancer reported no improvement in quality of life at short-term and long-term follow-ups (SMD=0.20; 95% CI: −0.05 to 0.45; and SMD=0.15; 95% CI: −0.11 to 0.41, respectively).50
Limitations
This study had some limitations that should be considered when interpreting its results. First, the people with sleep disturbances included in this review were adults with diverse health conditions including chronic insomnia, cancer and other conditions. Additionally, a variety of controls, including active and passive controls, were included. Therefore, statistical heterogeneity was identified in the meta-analysis assessing the effects of MBSR on reported sleep quality, depression, anxiety, stress and fatigue levels. However, although subgroup analyses were performed using a random-effects model, an unexplained heterogeneity remained. Second, most studies included in this review were deemed vulnerable to performance bias and detection bias in risk of bias assessment. Moreover, since a small number of studies were included in some subgroup analyses, further well-designed RCTs should be conducted. Finally, despite an extensive literature search, the risk of publication bias might have remained because only studies published in English and Korean were included.
Implications
This systematic review and meta-analysis showed that MBSR might be ineffective in improving objective and subjective sleep quality in patients with chronic insomnia and cancer. Moreover, most RCTs included in this review were small studies with a potential risk of bias due to deviations from the intended interventions and missing outcome data. Further well-designed large RCTs, with a low risk of bias, are required to determine whether MBSR, as a non-pharmacological intervention, helps improve sleep quality and mitigate sleep-related daytime impairments in adults with sleep disturbances.
Data availability statement
Data are available upon reasonable request. Our study uses published data only. The original contributions presented in the study are included in the article and online supplemental material, further inquiries can be directed to the corresponding author.
Ethics statements
Patient consent for publication
Ethics approval
Not applicable.
References
Supplementary materials
Supplementary Data
This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.
Footnotes
SMK and JMP contributed equally.
Contributors SMK and HJS conceptualised the study. SMK and JMP analysed the data. JK, JWN and HLK interpreted the data. SMK and JMP wrote the first drafts. HJS administrated the study and revised the manuscript. HJS takes responsibility for the decision to publish this study. All authors have read and approved the manuscript. HJS is guarantor of the study, contribution in study design, preparation of the manuscript, provided revisions to the scientific content of the manuscript.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.
Provenance and peer review Not commissioned; externally peer reviewed.
Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.