Sleep Restriction Therapy for Insomnia is associated with reduced objective total sleep time, increased daytime somnolence, and objectively-impaired vigilance: implications for the clinical management of Insomnia Disorder

Aims: Adverse-effects of psychological therapies are rarely recorded or considered. Sleep Restriction Therapy (SRT), an effective component of cognitive-behavioral therapy for insomnia, limits time-in-bed and may result in reduced total sleep time. Clinical evidence suggests that daytime impairment may be experienced by patients in the acute treatment period, yet there has been little systematic study of this possibility. Here, we investigated whether SRT is associated with reduced total sleep time, increased daytime somnolence and impaired vigilance. Design: Within-subjects, repeated measures treatment investigation with the addition of a matched good sleeper control group to permit between-group comparisons on performance measures. Setting: Sleep Research Laboratory Participants: Sixteen patients [10 female, Mean Age = 47.1 (10.8) yrs] with well defined psychophysiological insomnia (PI) and an age and gender-matched control group of good sleepers [GS, n=15; 10 female, mean age = 47.1 (10.5) yrs]. Interventions: Patients were treated with single component SRT over a 4-week protocol, comprising one main session for treatment delivery and weekly sleep window titration (weeks 1-4). Patients slept in the laboratory for two nights prior to treatment initiation and for three nights (SRT night 1, 8, 22) during the acute interventional phase. In addition, those with PI completed the psychomotor vigilance task (PVT) at seven defined time-points [day 0 (baseline), day 1,7,8,21,22 (acute treatment) and day 84 (3 months)]. The Epworth Sleepiness Scale (ESS) was completed at baseline, weeks 1-4, and at three months. Matched good sleepers completed the PVT at one single time-point to permit baseline performance comparisons with patients. Measurement and results: Subjective sleep outcomes and global insomnia severity significantly improved pre-to-post SRT. There was, however, a decrease in PSG defined total sleep time during acute implementation of SRT, by an average of 91 minutes on night 1, 78 minutes on night 8, and 69 minutes on night 22, relative to baseline (p’s<.001; effect size range=1.60-1.80). During SRT, PVT lapses were significantly increased from baseline (at 3/5 assessment points, all p<.05; effect size range=.69-.77), returning to baseline levels by three months (p=.43). A similar pattern was observed for RT, with RTs slowing during acute treatment (at 4/5 assessment points, all p<.05; effect size range=.57-.89) and returning to pre-treatment levels at three months (p=.88). While patients did not differ from good sleepers at baseline with respect to PVT performance (p’s<.20), between-group differences began to emerge during SRT, with patients showing relative impairment. Objective measures were paralleled by significant elevations in subjective daytime sleepiness at weeks 1, 2, and 3 (relative to baseline; all p<.05); by three months, sleepiness had returned to baseline (normative) levels (p=.65). Conclusion: For the first time we show that acute SRT is associated with reduced total sleep time, increased daytime sleepiness and objective performance impairment. Our data have important implications for implementation guidelines around the safe and effective delivery of CBT-I