Abstract
Study ObjectivesDigital cognitive behavioral therapy for insomnia (dCBT-I) is an effective treatment for insomnia. However, less is known about mediators of its benefits. The aim of the present study was to test if intraindividual variability in sleep (IIV) was reduced with dCBT-I, and whether any identified reduction was a mediator of dCBT-I on insomnia severity and psychological distress.MethodsIn a two-arm randomized controlled trial (RCT), 1720 adults with insomnia (dCBT-I = 867; patient education about sleep = 853) completed the Insomnia Severity Index (ISI), the Hospital Anxiety and Depression Scale (HADS) and sleep diaries, at baseline and 9-week follow-up. Changes in IIV were analyzed using linear mixed modeling followed by mediation analyses of ISI, HADS, and IIV in singular sleep metrics and composite measures (behavioral indices (BI-Z) and sleep disturbance indices (SI-Z)).ResultsdCBT-I was associated with reduced IIV across all singular sleep metrics, with the largest between-group effect sizes observed for sleep onset latency (SOL). Reduced IIV for SOL and wake after sleep onset had the overall greatest singular mediating effect. For composite measures, SI-Z mediated change in ISI (b = −0.74; 95% confidence interval (CI) −1.04 to −0.52; 13.3%) and HADS (b = −0.40; 95% CI −0.73 to −0.18; 29.2%), while BI-Z mediated minor changes.ConclusionReductions in IIV in key sleep metrics mediate significant changes in insomnia severity and especially psychological distress when using dCBT-I. These findings offer important evidence regarding the therapeutic action of dCBT-I and may guide the future development of this intervention.Clinical trials Name: Overcoming Insomnia: Impact on Sleep, Health and Work of Online CBT-I Registration number: NCT02558647 URL: https://clinicaltrials.gov/ct2/show/NCT02558647?cond=NCT02558647&draw=2&rank=1
Highlights
Insomnia is a major public health care concern that affects 10–12% of the general population in Western countries [1,2,3]
Our findings show that stabilizing voluntary sleep metrics do not appear to substantially mediate the effect of cognitive behavioral therapy for insomnia (CBT-I) itself, but are mediators in the stabilization of other sleep metrics, e.g. sleep onset latency, which in turn are important mediators of improvement in insomnia severity and especially psychological distress.These findings offer important knowledge regarding the role of stabilizing sleep in improving insomnia severity and further suggest that stabilizing sleep could be beneficial for populations with high levels of psychological distress
Our findings demonstrate that this reduction of intraindividual variability in sleep (IIV) is a therapeutic component of digital versions of CBT-I (dCBT-I) on insomnia severity and psychological distress
Summary
Insomnia is a major public health care concern that affects 10–12% of the general population in Western countries [1,2,3]. Several independent randomized controlled trials (RCTs) and meta-analyses [5, 6] have demonstrated the efficacy of cognitive behavioral therapy for insomnia (CBT-I) [7] in improving sleep and psychological outcomes [5]. The strength of evidence is such that CBT-I is the first-line treatment for insomnia [8,9,10]. To enhance translation of research into practice and address the clinical unmet need for interventions for insomnia, cost-efficient digital versions of CBT-I (dCBT-I) have been developed [11]. Similar to the face-to-face CBT-I, knowledge about the benefits of dCBT-I and specific populations who most benefit from this intervention currently exceeds our understanding of how the intervention works
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