Insomnia is more likely to persist than remit after a time of stress and uncertainty: a longitudinal cohort study examining trajectories and predictors of insomnia symptoms.

STUDY OBJECTIVES: The study aimed to characterize insomnia symptom trajectories over 12 months during a time of stress and uncertainty, the coronavirus disease 2019 (COVID-19) pandemic. It also aimed to investigate sleep and psychological predictors of persistent insomnia symptoms. METHODS: This longitudinal cohort study comprised 2069 participants with and without insomnia symptoms during the first year of the pandemic. Participants completed online surveys investigating sleep, insomnia, and mental health at four timepoints over 12 months (April 2020-May 2021). Additional trait-level cognitive/psychological questionnaires were administered at 3 months only. RESULTS: Six distinct classes of insomnia symptoms emerged: (1) severe persistent insomnia symptoms (21.65%), (2) moderate persistent insomnia symptoms (32.62%), (3) persistent good sleep (32.82%), (4) severe insomnia symptoms at baseline but remitting over time (2.27%), (5) moderate insomnia symptoms at baseline but remitting over time (7.78%), and (6) good sleep at baseline but deteriorating into insomnia symptoms over time (2.85%). Persistent insomnia trajectories were predicted by high levels of sleep reactivity, sleep effort, pre-sleep cognitive arousal, and depressive symptoms at baseline. A combination of high sleep reactivity and sleep effort reduced the odds of insomnia remitting. Higher sleep reactivity also predicted the deterioration of good sleep into insomnia symptoms over 12 months. Lastly, intolerance of uncertainty emerged as the only trait-level cognitive/psychological predictor of insomnia trajectory classes. CONCLUSIONS: Insomnia was more likely to persist than remit over the first year of the COVID-19 pandemic. Addressing sleep reactivity and sleep effort appears critical for reducing insomnia persistence rates after times of stress and uncertainty.