Abstract
IMPORTANCE: Daytime symptoms, including negative mood, fatigue, and cognitive impairment, are core features and diagnostic criteria for insomnia disorder. Historically, assessment of these daytime insomnia symptoms has relied on retrospective questionnaires with varying recall periods and that may lack sensitivity to detect subtle change attributable to insomnia treatment. OBJECTIVE: To use smartphone-based ecological momentary assessment (EMA) to determine the effect of insomnia pharmacotherapy on daytime insomnia symptoms. DESIGN, SETTING, AND PARTICIPANTS: This was a double-blind, placebo-controlled randomized clinical trial. All procedures were conducted remotely between October 9, 2023, and August 8, 2024. Following baseline assessment, participants were randomized to suvorexant or placebo, including 2 nights at 10 mg then 14 nights at 20 mg. Participants completed the Daytime Insomnia Symptoms Scale (DISS) 4 times per day (ie, 64 administrations over 16 days) and a posttreatment assessment. Participants were recruited from an academic center. Inclusion criteria were individuals aged 60 to 85 years, diagnosed with chronic insomnia per clinical interview, with moderate to severe insomnia symptoms (Insomnia Severity Index [ISI] ≥15), and owning a smartphone. Exclusion criteria were major untreated medical or psychiatric condition, contraindications for a dual-orexin receptor antagonist, refusal to discontinue other insomnia medications, or severe obstructive sleep apnea. Data were analyzed between September 6, 2024, and October 28, 2025. INTERVENTION: Suvorexant 20 mg nightly vs placebo. MAIN OUTCOMES AND MEASURES: The primary EMA measure was the DISS. During baseline and posttreatment assessments, participants also completed questionnaires assessing insomnia severity, sleepiness, fatigue, anxiety, and depression. RESULTS: Participants included 40 older adults (mean [SD] age, 67.9 [5.4] years; 36 [90%] women), with 20 participants randomized to suvorexant and 20 to placebo. There were no dropouts. The overall completion rate for EMA surveys was 93.3%. Relative to placebo, suvorexant reduced insomnia severity (mean [SD] change in ISI, -9.6 [5.4] vs -5.5 [6.8]; estimate [SE], 4.1 [1.9]; t = 2.1; df = 36; P = .04, effect size, 0.66 [95% CI, 0.02 to 1.30]). Based on retrospective questionnaires, no statistically significant between-group differences in daytime insomnia symptoms were detected. Based on EMA, significant between-group differences were detected in subjective cognition (χ24 = 11.12; P = .03) and fatigue (χ24 = 21.43; P = .003) at 1 or more times of day. CONCLUSIONS AND RELEVANCE: In this randomized clinical trial of older adults with insomnia, although traditional outcomes assessments detected no between-group differences, EMA was sensitive to detect effects of insomnia pharmacotherapy on daytime insomnia symptoms at various times of day, a critical gap in the literature. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT05908526.