Internight sleep variability: its clinical significance and responsiveness to treatment in primary and comorbid insomnia

Abstract

SUMMARYAlthough sleep diary and actigraphy data are usually collected daily for 1 or 2 weeks, traditional analytical approaches aggregate these data into mean values. Internight variability of sleep often accompanies insomnia. However, few studies have explored the relevance of this ÔconstructÕ in the context of diagnosis, clinical impact, treatment effects and ⁄ or whether having Ôvariable sleepÕ carries any prognostic significance. We explored these questions by conducting secondary analyses of data from a randomized clinical trial. The sample included primary (PI: n = 40) and comorbid insomnia (CMI: n = 41) sufferers receiving four biweekly sessions of cognitive-behavioural therapy (CBT) or sleep hygiene education. Using the within-subject standard deviations of diary-and actigraphy-derived measures collected for 2-week periods [sleep onset latency (SOL), wake after sleep onset (WASO), total sleep time (TST) and sleep efficiency (SE)], we found that CMI sufferers displayed more variable self-reported SOLs and SEs than PI sufferers. However, higher variability in diary and actigraphy-derived measures was related to poorer sleep quality only within the PI group, as measured by the Pittsburgh Sleep Quality Index (PSQI). Within both groups, the variability of diary-derived measures was reduced after CBT, but the variability of actigraphy-derived measures remained unchanged. Interestingly, the variability of actigraphy measures at baseline was correlated with PSQI scores at 6-month follow-up. Higher SOL variability was associated with worse treatment outcomes within the PI group, whereas higher WASO variability was correlated with better treatment outcomes within the CMI group. Sleep variability differences across insomnia diagnoses, along with their distinctive correlates, suggest that mechanisms underlying the sleep disruption ⁄ complaint and treatment response in both patient groups are distinct. Further studies are warranted to support variability as a useful metric in insomnia studies.

A Single Arm Pilot Trial of Brief Cognitive Behavioral Therapy for Insomnia in Adolescents with Physical and Psychiatric Comorbidities

“…Although several CBT-I trials have demonstrated improvement in both sleep diary and actigraphic variables, a number of studies have demonstrated changes in only sleep diary data. 31,32 Especially relevant to the current study, in Bootzin and Steven's trial of CBT-I in adolescents with comorbid insomnia and substance use, a similar phenomenon was observed in that sleep diary results indicated significant changes after treatment whereas actigraphy-measured sleep did not change. 13 The lack of change in actigraphic sleep data compared to the moderate to large changes in sleep-diary and self-report data in our trial could be reflective of several issues related to using actigraphy in context of a brief intervention.…”

Sleep, Sleep Disorders, and Mild Traumatic Brain Injury. What We Know and What We Need to Know: Findings from a National Working Group

“…Therefore, multiple methods are essential to capture both subjective and objective measures of sleep, preferably with serial assessment. In addition to assessing central tendency, within-subject variability and night-to-night variability of sleep patterns must also be considered, as these are increasingly recognized as important determinants of disease severity and treatment outcome [131][132][133][134].…”

Night-to-Night Sleep Variability in Older Adults With Chronic Insomnia: Mediators and Moderators in a Randomized Controlled Trial of Brief Behavioral Therapy (BBT-I)

“…These findings are consistent with prior studies in young and middle-aged adults. 13,14 Extending from previous research, this study showed that a 4-session BBT-I was efficacious in reducing sleep variability in older adults with chronic insomnia. The decreases in percentage in SOLs variability and TSTa variability were comparable to those in a prior study implementing a 4-session CBT-I in middle-aged adults.…”

“…Sanchez-Ortuno and Edinger found that higher baseline sleep variability was associated with worse sleep outcomes following CBT-I, 13 …”

“…The decreases in percentage in SOLs variability and TSTa variability were comparable to those in a prior study implementing a 4-session CBT-I in middle-aged adults. 13 The current study included a SMAC group that provided a more stringent test of the effects of the treatment of insomnia in reducing sleep variability than prior studies, in which a control group was not included. 4,13,14 A prior randomized controlled trial of a 12-month exercise intervention showed that SOLs variability significantly decreased in the intervention group, compared to the health education control group, by about 20% (~15 minutes) from baseline to posttreatment.…”