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. 2024 Mar 14;33(6):e14193. doi: 10.1111/jsr.14193

Digital cognitive behavioural therapy for insomnia reduces insomnia in nurses suffering from shift work disorder: A randomised‐controlled pilot trial

Johanna Ell 1,✉, Hanna A Brückner 2, Anna F Johann 1,3, Lisa Steinmetz 1, Lara J Güth 4, Bernd Feige 1, Heli Järnefelt 5, Annie Vallières 6,7,8, Lukas Frase 1,9, Katharina Domschke 1, Dieter Riemann 1,10, Dirk Lehr 2, Kai Spiegelhalder 1
PMCID: PMC11596998  PMID: 38485134

Summary

Insomnia is a primary symptom of shift work disorder, yet it remains undertreated. This randomised‐controlled pilot trial examined the efficacy of a digital, guided cognitive behavioural therapy for insomnia adapted to shift work (SleepCare) in nurses with shift work disorder. The hypothesis was that SleepCare reduces insomnia severity compared with a waitlist control condition. A total of 46 unmedicated nurses suffering from shift work disorder with insomnia (age: 39.7 ± 12.1 years; 80.4% female) were randomised to the SleepCare group or the waitlist control group. The primary outcome measure was the Insomnia Severity Index. Other questionnaires on sleep, mental health and occupational functioning, sleep diary data and actigraphy data were analysed as secondary outcomes. Assessments were conducted before (T0), after the intervention/waitlist period (T1), and 6 months after treatment completion (T2). The SleepCare group showed a significant reduction in insomnia severity from T0 to T1 compared with the control condition (β = −4.73, SE = 1.12, p < 0.001). Significant improvements were observed in sleepiness, dysfunctional beliefs about sleep, pre‐sleep arousal, sleep effort, self‐reported sleep efficiency and sleep onset latency. No significant effect was found in actigraphy data. Depressive and anxiety symptoms, cognitive irritation and work ability improved significantly. Overall, satisfaction and engagement with the intervention was high. SleepCare improved insomnia severity, sleep, mental health and occupational functioning. This is the first randomised‐controlled trial investigating the efficacy of digital cognitive behavioural therapy for insomnia in a population suffering from shift work disorder with insomnia. Future research should further explore these effects with larger sample sizes and active control conditions.

Keywords: cognitive behavioural therapy for insomnia, digital intervention, nurses, shift work disorder

1. INTRODUCTION

To ensure medical care for the ill and elderly, it is imperative to provide round‐the‐clock support for these population groups. Therefore, shift work is common in nurses, physicians and other health professionals. Shift work is defined as an atypical form of work schedule that deviates from the standard daytime work schedule, and can involve working hours between 19:00 hours and 06:00 hours (European Parliament and of the Council, 2003; International Labour Organization, 1990). Worldwide, approximately 20% of the working population are employed as shift workers (Bureau of Labor Statistics, 2019; Eurofound, 2017). Although shift work is inevitable in healthcare, systematic reviews and meta‐analyses suggest that shift work is associated with reduced work ability (Brown et al., 2020; Fischer et al., 2017; Kecklund & Axelsson, 2016; Rivera et al., 2020; Rosa et al., 2019), impaired mental health (Brown et al., 2020; Torquati et al., 2019) and the development of severe somatic diseases (e.g. cardiovascular diseases, cancer; Rivera et al., 2020; Sooriyaarachchi et al., 2022; Su et al., 2021). In addition, night shift work and rotating shift work are risk factors for the development of sleep disorders (Kerkhof, 2018; Linton et al., 2015), reduce overall sleep quality (De Cordova et al., 2012; Sallinen & Kecklund, 2010; Shen et al., 2016) and disrupt the circadian rhythm (Akerstedt, 2003; Dijk & Czeisler, 1995).

Current meta‐analytic data (Pallesen et al., 2021) suggest that 26.5% of shift workers suffer from shift work disorder (SWD), which is characterised by insomnia and/or excessive sleepiness associated with the work schedule for a time period of ≥ 3 months (American Academy of Sleep Medicine, 2014). Although SWD is considered to arise predominantly from circadian rhythm mismatch, the well‐known psychophysiological vicious circle of insomnia develops in many patients and may contribute to the maintenance and aggravation of insomnia symptoms (Bastille‐Denis et al., 2020; Cheng & Drake, 2018; Vallières et al., 2021). Therefore, the biopsychosocial approach that includes cognitive, emotional, social and behavioural factors may be beneficial for treatment outcomes (Costa, 2003; Vallières et al., 2015; Vallières & Bastille‐Denis, 2012).

In order to prevent and manage symptoms of SWD, several strategies are discussed on a legal (e.g. exemption from night shifts), organisational (e.g. designing appropriate shift schedules) and individual level (e.g. pharmacological or non‐pharmacological interventions). When considering treatment options on an individual level, it is notable that pharmacological interventions (e.g. stimulants, hypnotics, melatonin) have been the main focus of clinical practice and research for a long time (Liira et al., 2014, 2015; Neil‐Sztramko et al., 2014). Although non‐pharmacological interventions have also been developed (Slanger et al., 2016), their focus primarily lies on either improving circadian rhythm adaptation (e.g. light therapy, wearing sunglasses on the way home from a night shift) or reducing sleepiness (e.g. planned naps, consumption of coffee), while insomnia is not sufficiently addressed (Sack et al., 2007). However, insomnia is a primary symptom of SWD and, thus, should be clinically treated despite the lack of a gold‐standard. A non‐pharmacological approach that has been discussed recently in this context is cognitive behavioural therapy for insomnia (CBT‐I; Reynolds et al., 2023), which is the first‐line treatment for insomnia disorder according to current clinical guidelines (Edinger et al., 2021; Qaseem et al., 2016; Riemann et al., 2023). CBT‐I involves psychoeducation about sleep, including sleep hygiene practices, relaxation therapy, sleep restriction therapy, stimulus control therapy and cognitive therapy. There is robust evidence for the efficacy of CBT‐I for managing insomnia in non‐shift workers across different delivery modalities (Gao et al., 2022; Hertenstein et al., 2022; Van Straten et al., 2018). Data from a recent meta‐analysis of nine studies suggest that CBT‐I might also reduce insomnia symptoms in shift workers, but available evidence is insufficient to recommend CBT‐I for the treatment of this population due to methodological concerns and heterogeneity between studies (Reynolds et al., 2023). Most included studies were not designed as randomised‐controlled trials (RCTs; Jang et al., 2020; Järnefelt et al., 2014; Lee et al., 2014; Omeogu et al., 2020; Peter et al., 2019), some implemented only single components of CBT‐I (e.g. psychoeducation; Atlantis et al., 2006; Booker et al., 2022), did not adapt CBT‐I to the specific requirements of shift workers (Lee et al., 2014; Omeogu et al., 2020; Peter et al., 2019; Schiller et al., 2018), did not screen for insomnia in the recruitment process (Atlantis et al., 2006; Booker et al., 2022; Jang et al., 2020; Lee et al., 2014) or defined the target population somewhat imprecisely (Atlantis et al., 2006; Omeogu et al., 2020; Peter et al., 2019), and none of the studies reported the inclusion of people with lived experience in the research process to account for the specific needs of shift workers suffering from SWD. Therefore, RCTs that examine the efficacy of carefully designed interventions on patient‐reported and objective outcomes are needed to achieve a clearer evidence base regarding CBT‐I in the context of shift work.

Due to irregular working hours, shift workers also face particular difficulties in attending regular face‐to‐face appointments, whereas digital interventions may offer increased flexibility to address individual sleep problems independently of time and place. The existing literature indicates that digital CBT and CBT‐I can improve clinical outcomes in mental health in general as well as in insomnia disorder, especially when human support is provided (e.g. in the form of written feedback including clinical recommendations; Gao et al., 2022; Hasan et al., 2022; Moshe et al., 2021; Schueller et al., 2017).

The aim of the present study was to examine the efficacy of a digital, guided CBT‐I programme in nurses suffering from SWD with insomnia. For this purpose, together with people with lived experience, we designed a CBT‐I‐based intervention adapted to shift workers and conducted a RCT with insomnia severity as primary outcome. The hypothesis was that digital CBT‐I reduces insomnia severity compared with a waitlist control condition.

2. METHODS

This study is reported according to the CONSORT statement, and the extensions for non‐pharmacological and psychological interventions (Begg, 1996; Boutron et al., 2017; Montgomery et al., 2018).

2.1. Participants

Recruitment for this study was conducted between October 2021 and November 2022, during the COVID‐19‐pandemic. Participants were eligible for inclusion if they met the following criteria: (1) age between 18 and 65 years; (2) employment as a nurse; (3) rotating shift work during the entire study participation (working at least in a half‐time position) with at least 10% of the shifts being night shifts (defined as a minimum of 3 hr of working time between 22:00 hours and 06:00 hours); (4) a diagnosis of SWD with insomnia (with or without daytime sleepiness); (5) internet access; and (6) fluency in German language. Exclusion criteria were: (1) any other comorbid psychiatric or sleep disorder; (2) any severe or instable somatic disease that influences sleep; (3) intake of medication affecting sleep in the 2 weeks before or during study participation; (4) acute suicidality; (5) previous treatment with CBT‐I; (6) current psychotherapeutic treatment or being on a waitlist for psychotherapy; and (7) current participation in another health training programme to improve sleep.

2.2. Procedure and materials

The study flow chart of this parallel group RCT is presented in Figure 1. First, nurses were informed about the study via flyers, internal email distribution lists and social media accounts of hospitals within Southern Germany. Next, interested nurses contacted the study coordinator (author JE) via email, telephone or the study website, and were invited for a telephone‐based screening interview (60–90 min) conducted by a clinical psychologist specialised in sleep medicine (author JE). This interview consisted of the Shift Work Disorder Screening Tool (Barger et al., 2012), a semi‐structured interview regarding shift work and sleep‐related symptoms, as well as the MINI‐DIPS, a standardised screening instrument for psychological disorders (Margraf & Cwik, 2017). The diagnosis of SWD was established clinically by author JE based on the interview, and only participants with SWD with insomnia symptoms (with or without daytime sleepiness) were included in the study.

FIGURE 1.

FIGURE 1

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Flow diagram of the randomised‐controlled trial (RCT).

Included participants completed the baseline assessment (T0) consisting of the questionnaire battery outlined below, a standard sleep diary for the duration of 1 week (Carney et al., 2012), and 1 week of actigraphy (Movisens Light 3 Sensor; Movisens GmbH, Karlsruhe, Germany). Of note, participants were not allowed to wear actigraphy devices at work. The primary outcome of the trial was insomnia severity, assessed with the Insomnia Severity Index (ISI; Bastien, 2001). In addition, the following questionnaires were used at T0: regarding sleep parameters, the reduced Morningness–Eveningness Questionnaire (rMEQ; Adan & Almirall, 1991; Randler, 2013), Epworth Sleepiness Scale (ESS; Johns, 1991), Glasgow Sleep Effort Scale (GSES; Broomfield & Espie, 2005), brief version of the Dysfunctional Beliefs and Attitudes about Sleep Scale (DBAS‐16; Morin et al., 2007), and the Pre‐Sleep Arousal Scale (PSAS; Nicassio et al., 1985) were implemented. To assess mental health, the Beck Depression Inventory‐II (BDI‐II; Beck et al., 1996), State Trait Anxiety Inventory (STAI; Spielberger et al., 1983) and Perceived Stress Scale‐10 (PSS‐10; Cohen et al., 1983) were used; and to assess work‐related burden, the Work Ability Single‐Item‐Question (WAI; Ahlstrom et al., 2010), subscales “psychological detachment from work” and “relaxation” of the Recovery Experience Questionnaire (REQ; Sonnentag & Fritz, 2007), and subscale “cognitive irritation” of the Irritation Scale (Mohr et al., 2005) were implemented. All questionnaires demonstrated acceptable to excellent internal consistency in this sample at baseline. Comprehensive information regarding the characteristics of the employed questionnaires is available in Supplementary Table S1. Also, sociodemographic data (e.g. age, sex, education and shift work history) were collected at baseline. After completion of T0, participants were randomised to the treatment condition (SleepCare) or the waitlist control group using simple randomisation conducted by a person otherwise not involved in the project, thus ensuring allocation concealment. Due to the study design, blinding was not possible.

The post‐treatment/post‐waitlist assessment (T1) was conducted as soon as possible after the completion of the treatment/the 8‐week waitlist condition, including the same measurements as at T0 in the same order, with the exception of the rMEQ and the sociodemographic questions (baseline only). Engagement with the intervention was operationalised by the number of modules completed in the intervention group. For the assessment of feasibility and acceptability, patients from the treatment group were asked to complete a self‐developed questionnaire on their experience with the online programme, and to participate in a telephone‐based semi‐structured interview at T1 (15 minutes). In addition, participants were asked to answer the following questions online on a rating scale from 0 (not at all helpful/easy) to 100 (extremely helpful/easy) after the completion of every module of the intervention: “How helpful was this module for you?”, “How easy was it for you to work through the module?”.

To provide all participants with an opportunity for treatment regardless of group assignment, patients in the waitlist control condition received digital CBT‐I after T1. Because of this, follow‐up data were only collected in the treatment group at 6 months after treatment completion (T2). The T2 assessment included the same measurements as the T1 assessment in the same order.

The study was conducted in accordance with the Declaration of Helsinki, and was registered in the German Clinical Trials Register in October 2021 (https://www.drks.de/drks_web/; ID:DRKS00026770). The study protocol was approved by the local Institutional Review Board (Leuphana University of Lüneburg, EB‐Antrag_202007‐12‐Lehr_ONSEPS). Written informed consent was obtained from all patients prior to data collection.

2.3. Intervention

SleepCare is a digital programme developed as an interactive website and designed to target nurses suffering from SWD with insomnia. Two insomnia experts (authors DR, KS), an expert for e‐mental health (author DL) and two nurses with insomnia symptoms working shifts were engaged in the development of the digital intervention that adapts CBT‐I to the specific requirements of nurses with SWD with insomnia. The treatment consists of six modules that can be worked through by the participants themselves using an internet‐enabled device. Each module contains written information, explanation videos, interactive exercises for self‐reflection and skill‐building, experiences of three other fictitious nurses suffering from SWD with insomnia guiding the participants through the intervention (model nurses), and audio files (e.g. for relaxation therapy). Once one module is completed by the participants, they receive manual‐based individualised feedback in written form within the platform from a clinical psychologist trained in CBT‐I who participates in weekly sleep expert boards to discuss cases (author JE). SleepCare is combined with a digital sleep diary, which is provided via study smartphones, and assesses both daytime and night‐time sleep. In case of periods of inactivity longer than 10 days, participants are motivated to continue via text messages within the platform. Modifications of CBT‐I for SWD with insomnia include additional information about chronobiology, sleep hygiene for daytime sleep (Sack et al., 2007; Wickwire et al., 2017; Wright et al., 2013), strategies to stay awake during night shifts (Gurubhagavatula et al., 2021; Sack et al., 2007; Wickwire et al., 2017; Wright et al., 2013), recommendations for shift work schedules following current German guidelines (Deutsche Gesellschaft für Arbeitsmedizin und Umweltmedizin, 2020), a module on the interaction between sleep, shift schedules and social life (Arlinghaus et al., 2019; Bambra et al., 2008; Gurubhagavatula et al., 2021; Kecklund & Axelsson, 2016; Monk, 1988), the separate calculation of sleep windows for each shift in the context of sleep restriction therapy, and anchor sleep to enhance consistency of sleep timing even when schedules change (Minors & Waterhouse, 1981; Wickwire et al., 2017; Wright et al., 2013). For a detailed overview of the content and structure of SleepCare, see Table 1 and the TIDieR checklist (Hoffmann et al., 2014) in the Supplementary Information.

TABLE 1.

Modules of SleepCare.

Modules Content
Modul 1: Introduction

  • Getting to know the structure of SleepCare

  • Psychoeducation about sleep, chronobiology and shift work

  • Explanatory model for the development and maintenance of one's own sleep difficulties

  • Identifying personal resources

Module 2: Sleep hygiene and relaxation
  • Sleep hygiene
  • Recommendations for daytime sleep
  • Strategies to stay awake during night shifts
  • Recommendations for shift work schedules
  • Relaxation therapy

Module 3:

Sleep restriction therapy

  • Introduction to sleep restriction therapy

  • Scheduling of the sleep window for each shift

  • Introducing anchor sleep (enhancing sleep consistency by implementing a sleep episode of 4 hr slept at the same time after morning shifts or evening shifts and on days off)

  • Preparing for barriers during sleep restriction therapy

Module 4:

Shift work and social life

  • Dealing with adverse events and challenges of sleep restriction therapy

  • Balance between sleep, social life and shift work

  • Focus on positive work interactions

Module 5:

Cognitive therapy

  • ABC model (according to A. Ellis)

  • Changing negative sleep‐related thoughts to more constructive ones

  • Cognitive strategies to manage worry and rumination in bed

Module 6:

Follow‐up and feedback

  • Personalised evaluation of sleep restriction therapy

  • Relapse prevention

  • Download of a summary of the content of all modules
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2.4. Statistical analyses

For descriptive data at T0, we calculated means and standard deviations for continuous variables and proportions for categorical variables. Efficacy analyses followed intention‐to‐treat principles, and missing data at T1 and T2 were imputed using the last‐observation‐carried‐forward method, which is a conservative approach suitable for conditions that may exhibit variations or improvement over time rather than a consistent deterioration (European Medicines Agency, 2010). Pre‐to‐post‐treatment effects were analysed using linear mixed‐models with the independent variables “group” (SleepCare versus waitlist), “time” (T1 versus T0), the “group × time” interaction and “participant” (study ID) as random effect. For the analysis of the long‐term stability of treatment effects in the SleepCare group, paired t‐tests were used comparing 6‐month follow‐up data (T2) with post‐treatment data (T1). To evaluate treatment/waitlist response per group, responders were defined as participants with an ISI change score (T1 – T0) of ≥ 7. In addition, participants were considered remitters if their ISI score was < 8 (corresponding to the “no insomnia” category; Morin et al., 2009).

The ISI score at T1 was chosen as the primary outcome. Secondary outcomes included: (1) all other above‐mentioned questionnaires on sleep, mental health and work; (2) sleep diary‐ and actigraphy‐derived total sleep time (TST), sleep efficiency (SE), sleep onset latency (SOL) and wake after sleep onset (WASO); as well as (3) the mean activity during sleep assessed by actigraphy. Of note, ISI scores as well as sleep diary‐ and actigraphy‐derived variables referred to both night‐time sleep and daytime sleep after night shifts.

During manual validation of sleep diary data, a total of eight sleep periods (from three participants) with obviously unrealistic values (e.g. self‐reported TST of 790 min with corresponding self‐reported time in bed of 1 min) were excluded. For a total of six sleep periods with 100% < SE < 130%, SE was set to 100%. Preprocessing of actigraphy data was performed using the package pyActigraphy (Hammad et al., 2021) in Python 3 (https://www.python.org/). The data were then manually checked for plausibility. Data were removed when they were categorised as not plausible (e.g. actigraphy data showing TST of zero minutes, while sleep diary data for the corresponding night showed TST of 480 min and sleep quality was rated as “very high”), or when the sensor did not record data due to technical issues. When actigraphy data were missing for more than 4 of 7 days at T0, the participants were excluded from the actigraphy analyses (T0). When actigraphy data were missing for more than 4 of 7 days at T1 or T2, the last‐observation‐carried‐forward method was used. Also, mean activity during sleep was log‐transformed to reduce skewness. The number of completed modules was used for assessing engagement with the intervention. For user experience analysis, means and standard deviations for continuous variables and proportions for categorical variables for the corresponding self‐developed questions were calculated. Moreover, narrative summaries were derived from qualitative feedback given in the telephone‐based interviews. All analyses were performed using the statistical software R version 4.3.2 (http://www.R-project.org/), with the level of significance set at p < 0.05 (two‐tailed).

The a priori power analysis was based on the assumption that CBT‐I has the potential to result in medium‐sized effects in nurses with SWD with insomnia (Reynolds et al., 2023). The analysis for the within‐between interaction (f = 0.25) with a power of (1 – β) = 0.9 at an alpha error level of 0.05 and a correlation among repeated measures r = 0.5 conducted with the G*Power tool (version 3.1.9.7; Faul et al., 2007) resulted in a sample size of n = 46 subjects (n = 23 per group).

3. RESULTS

3.1. Study population

The study sample included 46 shift‐working nurses suffering from SWD with insomnia. Mean age at T0 was 39.7 years (SD = 12.1 years), 37 (80.4%) participants were female, and mean ISI at baseline was 15.4 (SD = 4.2). Detailed descriptive information of the study population is presented in Table 2. In the SleepCare group (n = 23), 16 (69.6%) participants completed all six modules, three participants (13.0%) completed the first three modules, one participant (4.3%) completed the first two modules, two participants (8.7%) completed the first module, and one participant (4.3%) logged in without completing any module (Figure 1).

TABLE 2.

Participant baseline characteristics.

Total SleepCare Waitlist
(N = 46) (n = 23) (n = 23)
Age (years) 39.7 (12.1) 39.4 (11.9) 40.1 (12.5)
Sex (female) 37 (80.4%) 18 (78.3%) 19 (82.6%)
BMI (kg/m2) 25.4 (4.4) 25.4 (4.7) 25.4 (4.2)
Education
High school or higher 29 (60.9%) 15 (65.2%) 14 (60.9%)
Secondary school 17 (39.1%) 8 (34.8%) 9 (39.1%)
Married 16 (34.8%) 9 (39.1%) 7 (30.4%)
Children in household 17 (37.0%) 7 (30.4%) 10 (43.5%)
Working min. 80% 39 (84.8%) 22 (95.7%) 17 (73.9%)
Working hours per week 35.2 (5.8) 36.6 (5.0) 33.8 (6.2)
Hours worked per shift 8.1 (0.4) 8.1 (0.4) 8.0 (0.4)
Number of night shifts per month 4.5 (2.8) 4.4 (2.4) 4.6 (3.0)
Number of different shifts worked
2 4 (8.7%) 2 (4.3%) 2 (4.3%)
3 37 (80.4%) 17 (40.0%) 20 (43.5%)
4 2 (4.3%) 1 (2.2%) 1 (2.2%)
5 2 (4.3%) 2 (4.3%) 0 (0.0%)
6 1 (2.2%) 1 (2.2%) 0 (0.0%)
Working irregular schedules a 29 (63.0%) 16 (69.6%) 13 (56.5%)
Years working shifts 15.0 (8.0) 16.3 (8.5) 13.7 (7.5)
Years suffering from SWD with insomnia 7.4 (9.6) 5.6 (6.3) 9.2 (11.8)
Working with COVID patients 30 (65.2%) 15 (65.2%) 15 (65.2%)
Reporting moderate to strong COVID‐related burden 34 (73.9%) 15 (65.2%) 19 (82.6%)
Internet use on a daily basis 46 (100%) 23 (100%) 23 (100%)
Prior experience with online‐based interventions 3 (6.5%) 1 (4.3%) 2 (8.7%)
ISI 15.4 (4.2) 15.5 (4.5) 15.3 (3.9)
rMEQ b 13.8 (3.8) 13.1 (2.9) 14.4 (4.5)
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Note: All data are presented as mean (SD) or n (%).

Abbreviations: BMI, body mass index; COVID, Coronavirus SARS‐CoV‐2; ISI, Insomnia Severity Index; rMEQ, reduced Morningness–Eveningness Questionnaire; SWD, shift work disorder.

a

Self‐reported order of different shifts that varies from week to week.

b

Values of a rMEQ total score ≤ 11 correspond to “evening types” and values ≥ 18 correspond to “morning types”.

3.2. Primary outcome

Regarding ISI scores, the interaction effect group × time was significant (β = −4.73, SE = 1.12, p < 0.001), indicating that the SleepCare group exhibited a significantly greater decrease from T0 to T1 (from M = 15.5 to M = 10.1) compared with the waitlist control group (from M = 15.3 to M = 14.6; Figure 2; Table 3). In the SleepCare group, response rate at T1 was 34.8% (n = 8) and the remission rate was 39.1% (n = 9). In the waitlist control group, no participant was remitted at T1 and response rate was 4.3% (n = 1).

FIGURE 2.

FIGURE 2

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Effects on insomnia severity compared between groups.

TABLE 3.

Effects on self‐reported sleep, mental health and occupational functioning (n = 46)

Group Pre‐to‐post comparison between groups (T1 versus T0) Stability of treatment effects (T2 versus T1)
SleepCare (n = 23) Waitlist (n = 23) Group × time Effect size Within‐subject comparison
Outcome T0 T1 T2 T0 T1 ß SE p Cohens' d t p
ISI 15.5 (4.5) 10.1 (6.4) 9.4 (6.0) 15.3 (3.9) 14.6 (3.5) −4.73 1.12 < 0.001 1.25 0.89 0.383
ESS 8.0 (4.6) 6.0 (4.4) 6.4 (4.4) 9.4 (3.9) 9.5 (3.9) −2.13 0.93 0.027 0.68 −0.92 0.367
DBAS‐16 4.5 (1.3) 3.4 (1.9) 3.0 (1.8) 4.7 (1.8) 4.5 (1.7) −0.87 0.28 0.003 0.92 1.90 0.071
PSAS 34.1 (11.2) 29.1 (12.1) 27.5 (11.4) 32.7 (10.8) 33.7 (9.6) −5.96 2.06 0.006 0.85 1.02 0.318
Somatic 12.9 (4.8) 13.0 (5.1) 12.2 (5.1) 12.9 (5.0) 13.6 (4.5) −0.61 1.12 0.589 0.16 0.96 0.349
Cognitive 21.2 (7.7) 16.2 (7.5) 15.3 (6.9) 19.8 (7.3) 20.1 (6.2) −5.35 1.44 0.001 1.10 0.94 0.359
GSES 6.1 (2.5) 4.6 (3.0) 3.8 (3.0) 6.5 (3.1) 7.2 (2.8) −2.22 0.53 < 0.001 1.24 1.48 0.154
BDI‐II 9.7 (7.0) 7.0 (6.8) 6.0 (6.1) 8.8 (4.8) 9.1 (5.6) −3.00 1.35 0.032 0.65 1.21 0.238
STAI‐state 41.1 (10.1) 37.6 (11.8) 36.5 (11.7) 37.2 (7.6) 38.6 (7.9) −4.87 2.08 0.024 0.69 0.78 0.445

STAI‐trait

PSS‐10

Irritation Scale – cognitive

 41.7 (10.0) 39.6 (11.9) 38.6 (11.2) 39.7 (8.3) 41.0 (9.1) −3.39 2.12 0.117 0.47 0.90 0.379
18.2 (7.3) 16.6 (8.5) 16.0 (8.9) 17.6 (6.1) 17.4 (6.8) −1.35 1.59 0.402 0.31 0.71 0.486
11.0 (4.8) 8.1 (4.7) 8.2 (4.8) 11.7 (5.0) 12.0 (5.2) −3.17 0.74 < 0.001 1.27 −0.14 0.888
REQ – cognitive detachment 12.7 (4.2) 13.9 (3.7) 14.2 (4.3) 12.9 (4.2) 12.5 (3.4) 1.61 0.83 0.059 0.57 −0.56 0.580
REQ – relaxation 12.8 (3.7) 13.7 (3.8) 14.9 (4.5) 14.7 (3.0) 14.3 (3.3) 1.39 0.81 0.092 0.51 −2.38 0.027
WAI 6.8 (1.8) 7.4 (1.9) 7.4 (2.1) 7.5 (1.6) 7.4 (1.2) 0.74 0.34 0.033 0.65 −0.46 0.648
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Note: Descriptive data by group and measurement time are presented as mean (SD).

Abbreviations: BDI‐II, Beck Depression Inventory‐II; DBAS‐16, brief version of the Dysfunctional Beliefs and Attitudes about Sleep Scale; ESS, Epworth Sleepiness Scale; GSES, Glasgow Sleep Effort Scale; ISI, Insomnia Severity Index; PSAS, Pre‐Sleep Arousal Scale; PSS‐10, Perceived Stress Scale‐10; REQ, Recovery Experience Questionnaire; STAI, State Trait Anxiety Inventory; WAI, Work Ability Index.

3.3. Secondary outcomes

Results of the statistical models for all outcome measures are presented in Table 3 (questionnaires), Table 4 (sleep diary) and Table 5 (actigraphy).

TABLE 4.

Effects on sleep diary data (n = 45)

Group Pre‐to‐post comparison between groups (T1 versus T0) Stability of treatment effects (T2 versus T1)
SleepCare (n = 23) Waitlist (n = 22) Group × time Effect size Within‐subject comparison
Outcome T0 T1 T2 T0 T1 ß SE p Cohens' d t p
SE (%) 80.5 (7.7) 85.6 (9.8) 84.9 (9.6) 84.6 (13.9) 83.3 (9.0) 0.07 0.03 0.017 0.74 0.59 0.562
TST (min) 403.1 (57.2) 394.9 (70.0) 408.9 (58.5) 390.8 (81.5) 416.6 (88.2) −33.95 21.65 0.124 0.47 −1.53 0.140
SOL (min) 29.1 (14.9) 18.4 (16.0) 20.7 (14.4) 23.4 (26.3) 22.9 (14.2) −10.19 3.99 0.014 0.76 −1.20 0.244
WASO (min) 29.0 (30.1) 19.5 (30.5) 20.8 (30.6) 24.8 (31.7) 24.4 (29.8) −9.14 6.30 0.154 0.43 −0.35 0.733
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Note: Descriptive data by group and measurement time are presented as mean (SD).

Abbreviations: SE, sleep efficiency; SOL, sleep onset latency; TST, total sleep time; WASO, wake after sleep onset.

TABLE 5.

Effects on actigraphy data (n = 38)

Group Pre‐to‐post comparison between groups (T1 versus T0) Stability of treatment effects (T2 versus T1)
SleepCare (n = 19) Waitlist (n = 19) Group × time Effect size Within‐subject comparison
Outcome T0 T1 T2 T0 T1 ß SE p Cohens' d t p
SE (%) 81.6 (13.6) 86.3 (9.1) 85.8 (12.3) 84.9 (15.9) 82.2 (18.6) 0.07 0.04 0.069 0.61 0.20 0.846
TST (min) 414.1 (76.0) 408.5 (81.5) 407.2 (55.7) 410.5 (98.5) 416.5 (103.8) −11.58 30.83 0.709 0.12 0.06 0.950
SOL (min) 75.2 (57.3) 52.7 (37.6) 52.5 (50.8) 65.5 (90.2) 64.0 (65.6) −21.05 20.04 0.301 0.34 0.01 0.991
WASO (min) 20.9 (31.9) 14.8 (36.6) 17.1 (37.0) 17.7 (31.5) 39.4 (77.1) −27.78 17.39 0.119 0.52 −0.92 0.370
Mean activity during sleep a −6.7 (0.2) −6.7 (0.2) −6.6 (0.2) −6.6 (0.2) −6.6 (0.1) −0.04 0.05 0.369 0.30 −0.69 0.497
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Note: Descriptive data by group and measurement time are presented as mean (SD).

a

Data of activity during sleep are log‐transformed.

Abbreviations: SE, sleep efficiency; SOL, sleep‐onset latency; TST, total sleep time; WASO, wake after sleep onset.

With respect to questionnaires on sleep and mental health, there were significant group × time interaction effects for the ESS (β = −2.13, SE = 0.93, p = 0.027), DBAS (β = −0.87, SE = 0.28, p = 0.003), GSES (β = −2.22, SE = 0.53, p < 0.001), the cognitive subscale of the PSAS (β = −5.35, SE = 1.44, p = 0.001), BDI‐II (β = −3.00, SE = 1.35, p = 0.032) and STAI‐state (β = −4.87, SE = 2.08, p = 0.024), indicating a greater degree of improvement in the SleepCare group for all of these outcomes. There were no significant group × time effects for the somatic subscales of the PSAS, the PSS and the STAI‐trait.

With respect to work‐related questionnaires, there were significant group × time interaction effects for the WAI (β = 0.74, SE = 0.34, p = 0.033) and the cognitive irritation scale (β = −3.17, SE = 0.74, p < 0.001), indicating a greater degree of improvement in the SleepCare group. There were no significant group × time effects for either the “cognitive detachment” subscale or the “relaxation” subscale of the REQ.

For the analyses of the sleep diary, data of n = 45 were available. There were significant group × time interaction effects for SE (β = 0.07, SE = 0.03, p = 0.017) and SOL (β = −10.19, SE = 3.99, p = 0.014), indicating a greater degree of improvement in the SleepCare group. There were no significant group × time effects for TST or WASO.

For the actigraphy analyses, data of n = 38 participants (n = 19 per group) were available. There were no significant group × time effects for any of the outcomes.

3.4. Stability of effects at follow‐up

Regarding stability of the results in the SleepCare group, there were no significant differences between T1 and T2 for all outcomes, with the exception of the “relaxation” subscale of the REQ (t = −2.38, p = 0.027). This tentatively suggests stability of all outcomes for a duration of 6 months, and even an improvement on the “relaxation” subscale of the REQ at follow‐up (Tables 3, 4, 5). The remission rate remained 39.1% (n = 9) at T2.

3.5. Feasibility and acceptability

The questionnaire on feasibility and acceptability was completed by n = 19 participants of the SleepCare group. Eighteen (94.7%) of the respondents were satisfied or highly satisfied with the intervention in general, and rated the technical feasibility as high or very high. Seventeen (89.5%) participants valued the independency of location and time, and 14 (73.7%) rated the intervention as easy to integrate in their daily lives. Sixteen (84.2%) of the respondents rated the extent of personal contact to be sufficient. Results of the questionnaire are presented in Supplementary Figure S1. The fifth module with the focus on cognitive therapy (M = 74.7; SD = 27.0) and the sixth module with an overview of the whole intervention (M = 75.1; SD = 21.9) were rated as most helpful, while the fourth module with the focus on social life and sleep (M = 59.1; SD = 35.8) was rated as least helpful. The first module focusing on psychoeducation (M = 83.0; SD = 17.6) and the sixth module (M = 84.9; SD = 17.0) were rated as the most feasible, and the fifth module (M = 63.8; SD = 30.7) as the least feasible module (Supplementary Table S2). Telephone‐based interviews after intervention were conducted with n = 14 participants (Supplementary Table S3). The treatment components that were most frequently mentioned as helpful were relaxation therapy (n = 7), psychoeducation and sleep hygiene (n = 7), sleep restriction therapy (n = 6), exercises for self‐reflection (n = 6), and the individualised guidance during treatment (n = 6). The treatment component most frequently mentioned as being challenging was sleep restriction therapy (n = 6).

4. CONCLUSIONS

This is the first RCT investigating the efficacy of digital CBT‐I in a population suffering from SWD with insomnia. The aim of this RCT was to investigate the efficacy of the digital, guided CBT‐I programme SleepCare in nurses suffering from SWD with insomnia. Our results showed a robust and sustained improvement of insomnia severity, and several other indicators of impairment in sleep, mental health and occupational functioning in the intervention group compared with the waitlist control group. However, there were no significant effects of the intervention on actigraphically measured sleep parameters. Engagement with the intervention, perceived feasibility and overall satisfaction with SleepCare were high in the intervention group.

The average reduction of 5.4 points on the ISI observed in the SleepCare group from pre‐to‐post‐treatment exceeds the average effect of 3.1 points reported in a recent meta‐analysis on CBT‐I in shift workers (Reynolds et al., 2023), and the effect size of 1.25 for the primary outcome suggests high efficacy. There are some possible explanations for this. First, unlike the interventions of some of the previous trials, the SleepCare programme included all components of CBT‐I that have been shown to be effective in non‐shift workers with insomnia disorder. Second, SleepCare included personalised guidance that may be beneficial in the context of digital interventions (Moshe et al., 2021). And third, people with lived experience were involved in the development of SleepCare accounting for the specific needs of nurses suffering from SWD with insomnia.

In terms of secondary outcomes, SleepCare also had significant immediate and sustained positive effects on daytime sleepiness, dysfunctional beliefs and attitudes about sleep, sleep effort, cognitive arousal, sleep diary‐derived SE and SOL, as well as depression and anxiety. These findings largely parallel those reported for CBT‐I in non‐shift workers, which also leads to improvements in a number of variables related to sleep and mental health (Ballesio et al., 2021; Benz et al., 2020; Hertenstein et al., 2022; Thakral et al., 2020). Moreover, this study corroborates preliminary findings from within‐subject investigations (Jang et al., 2020; Järnefelt et al., 2012; Lee et al., 2014; Murray et al., 2023; Peter et al., 2019; Vallières et al., 2015) and RCTs (Atlantis et al., 2006; Booker et al., 2022) that have identified beneficial effects of CBT‐I on additional sleep‐related and mental health‐related outcomes in shift workers.

In addition to this, SleepCare had also positive effects on occupational functioning. Some studies have previously assessed work‐related outcomes of CBT‐I, and suggested positive effects on productivity, presenteeism and job burnout (Vega‐Escaño et al., 2020). In the context of shift work, only one RCT examined the effects of CBT‐I on sick leave, with results indicating no decrease in nurses with SWD (Booker et al., 2022). The current study adds to this literature by showing medium‐to‐large‐sized effects for work ability and cognitive irritation as an indicator of occupational strain, but no significant effect for detachment and relaxation, measured by the REQ. While the precise reason for this pattern of results remains unclear, the data support that at least some aspects of occupational functioning benefit from insomnia treatment in shift workers. More research, however, appears to be warranted given that potential effects of CBT‐I on occupational functioning are of obvious clinical and societal importance (Kucharczyk et al., 2012).

There were no significant effects of SleepCare on actigraphy‐derived objective sleep parameters, which is in line with the results of other trials examining CBT‐I in the context of shift work (Järnefelt et al., 2012, 2020; Lee et al., 2014; Schiller et al., 2018). This result further supports the hypothesis that CBT‐I leads to more pronounced effects in the patient‐reported compared with the objective domain (Mitchell et al., 2019). In the most recent meta‐analysis on objective sleep outcomes of CBT‐I in non‐shift workers, there was even a significant decrease in actigraphically determined TST at post‐treatment and follow‐up (Mitchell et al., 2019). However, it should also be mentioned that there are rather few CBT‐I trials that included objective outcomes, and the current analysis was somewhat limited by the fact that participants were not allowed to wear actigraphy devices at work potentially resulting in an increased overall uncertainty in actigraphy‐derived sleep and wake detection in this sample.

Given that the remission rate was only 39% in the intervention group, the analysis of feasibility and acceptability as well as the qualitative interviews may aid in optimising SleepCare. In particular, these data suggest that the module on social life and sleep may be removed from the intervention or offered as an optional module, with an expanded focus on cognitive therapy instead. Moreover, because the individualised guidance was rated as very helpful, even more intensive communication may be established between patients and therapists. Of course, the persistent negative effects of shift work on sleep may inevitably limit the efficacy of CBT‐I in patients with SWD and insomnia.

This study has a number of strengths. First, we used a comprehensive screening for SWD with insomnia and study eligibility, which enhanced data quality and internal validity of the current trial. Second, by employing both patient‐reported and objective measures of sleep, we were able to provide a comprehensive assessment of the efficacy of CBT‐I in SWD with insomnia. Third, the dropout rate within the SleepCare group was low (17.4%; cf. Zachariae et al., 2016) and engagement with the intervention was high (69.6% completed all six sessions), which may have been a result of including people with lived experiences in the programme's development and the provision of high‐quality therapeutic support during treatment. However, it is also important to acknowledge certain limitations of the present study, including a relatively small sample size and the use of a waitlist group, which may have increased the observed effect sizes. In addition, shift schedules were very different between participants, increasing the error variance in the outcome variables of the present study. Finally, the results might not be generalisable to all shift workers due to differences in work environments and shift schedules between nurses and other occupations involving shift work.

In summary, in this RCT, SleepCare improved insomnia severity, sleep, mental health and occupational functioning in nurses suffering from SWD with insomnia. In light of these promising results, future studies may include larger sample sizes and use an active control condition as comparator. Digital CBT‐I may be also combined with in‐person psychotherapeutic sessions, other evidence‐based chronobiological interventions (e.g. light therapy) or organisational interventions (e.g. shift scheduling accounting for personal preferences, age and chronotype).

AUTHOR CONTRIBUTIONS

Johanna Ell: Writing – original draft; investigation; conceptualization; methodology; formal analysis; project administration; validation; visualization. Hanna A. Brückner: Writing – review and editing; visualization. Anna F. Johann: Writing – review and editing. Lisa Steinmetz: Writing – review and editing. Lara J. Güth: Writing – review and editing. Bernd Feige: Methodology; writing – review and editing; data curation. Heli Järnefelt: Writing – review and editing. Annie Vallières: Writing – review and editing. Lukas Frase: Writing – review and editing. Katharina Domschke: Writing – review and editing. Dieter Riemann: Writing – review and editing; visualization. Dirk Lehr: Writing – review and editing; supervision. Kai Spiegelhalder: Supervision; formal analysis; conceptualization; funding acquisition; methodology; resources.

CONFLICT OF INTEREST STATEMENT

JE: financial disclosure: none; non‐financial disclosure: none. HB: financial disclosure: none; non‐financial disclosure: none. AFJ: financial disclosure: none; non‐financial disclosure: none. LS: financial disclosure: none; non‐financial disclosure: none. LJG: financial disclosure: none; non‐financial disclosure: none. BF: financial disclosure: none; non‐financial disclosure: none. HJ: financial disclosure: none; non‐financial disclosure: none. AV: financial disclosure: has grants from the Canadian Social Sciences and Humanities Research Council (SSHRC: #125553), the Canadian Institutes of Health Research (PJK‐179821), and the New Frontiers in Research Fund (#NFRFR‐2021‐00392) that are not related to the present study, and a researcher‐initiated grant from EISAI Inc. (New Jersey) not related to the present study; non‐financial disclosure: none. LF: financial disclosure: none; non‐financial disclosure: none. KD: in the past 3 years: member of the Steering Committee Neurosciences, Janssen‐Cilag GmbH, and speaker's honoraria from Janssen‐Cilag GmbH; board member of the Freiburg Training Institute for Behavioural Therapy (FAVT GmbH). DR: financial disclosure: none; non‐financial disclosure: none. DL: financial disclosure: none; non‐financial disclosure: none. KS: financial disclosure: none; non‐financial disclosure: none.

INSTITUTIONAL REVIEW BOARD STATEMENT

The study protocol was approved by the local Institutional Review Board of the Leuphana University of Lüneburg (“EB‐Antrag_202007‐12‐Lehr_ONSEPS”).

PATIENT CONSENT STATEMENT

Written informed consent was obtained from all participants prior to data collection.

Supporting information

DATA S1. Supplementary Information.

JSR-33-e14193-s001.pdf (646.2KB, pdf)

ACKNOWLEDGEMENTS

This project was supported by the Hans Böckler Foundation, which is a non‐profit organisation of the German Federation of Trade Unions. The authors thank Dorothea Ell, Theresia Ell and Christopher Theis for translating the Shift Work Disorder Screening Tool into German based on the committee‐based approach (Behr, 2018). Open Access funding enabled and organized by Projekt DEAL.

Ell, J. , Brückner, H. A. , Johann, A. F. , Steinmetz, L. , Güth, L. J. , Feige, B. , Järnefelt, H. , Vallières, A. , Frase, L. , Domschke, K. , Riemann, D. , Lehr, D. , & Spiegelhalder, K. (2024). Digital cognitive behavioural therapy for insomnia reduces insomnia in nurses suffering from shift work disorder: A randomised‐controlled pilot trial. Journal of Sleep Research, 33(6), e14193. 10.1111/jsr.14193

Pre‐registration of this trial: 18 October 2021 at German Clinical Trials Register (https://drks.de/search/de/trial/DRKS00026770); ID: DRKS00026770.

DATA AVAILABILITY STATEMENT

The data that support the findings of this study are available from the corresponding author upon reasonable request.

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Supplementary Materials

DATA S1. Supplementary Information.

JSR-33-e14193-s001.pdf (646.2KB, pdf)

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

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