Eligible participants were adult patients with a diagnosis of insomnia disorder recruited from a sleep clinic provided via public mental health services in Norway. The Insomnia Severity Index (ISI) was the primary outcome measure. The non-inferiority margin was defined a priori as 2.0 points on the ISI at week 33.
Individuals were randomized to FtF CBT-I (n=52) or dCBT-I (n=49); mean baseline ISI scores were 18.4 (SD 3.7) and 19.4 (SD 4.1) respectively. At week 33, the mean scores were 8.9 (SD 6.0) and 12.3 (SD 6.9) respectively. There was a significant time effect for both interventions (p<0.001); and the mean difference in ISI at week 33 was -2.8 (95% CI: -4.8 to -0.8; p=0.007, Cohen's d=0.7), and -4.6 at week 9 (95% CI -6.6 to -2.7; p<0.001), Cohen's d=1.2.
At the primary endpoint at week 33, the 95% CI of the estimated treatment difference included the non-inferiority margin and was wholly to the left of zero. Thus, this result is inconclusive regarding the possible inferiority or non-inferiority of dCBT-I over FtF CBT-I, but dCBT-I performed significantly worse than FtF CBT-I. At week 9, dCBT-I was inferior to FtF CBT-I as the 95% CI was fully outside the non-inferiority margin. These findings highlight the need for more clinical research to clarify the optimal application, dissemination, and implementation of dCBT-I.
© Sleep Research Society 2021. Published by Oxford University Press on behalf of the Sleep Research Society.