Towards quantitative cutoffs for insomnia: how current diagnostic criteria mischaracterize remission

Although sleep symptoms of insomnia can be quantified, none of the current diagnostic systems stipulate quantitative cutoffs for sleep-onset latency (SOL) or wake time after sleep onset (WASO). Diagnoses are based instead on idiographic patient reports of "difficulty" falling/staying asleep. Therefore, we examined whether remission of insomnia as per the diagnostic criteria results from a normalization of quantitative sleep disturbance, or if it is simply reflective of tolerance to sleep symptoms.

This study involved a yearlong prospective investigation of 649 adults (48.1 ± 11.6 years; 69.3% female) with DSM-5-based insomnia. Participants completed measures of sleep disturbance, perceived sleep-related distress, daytime sleepiness, functional impairment, and workplace productivity at baseline and follow-up one year later.

A total of 271 participants no longer met the DSM-5-based insomnia criteria at follow-up. However, 66% of these remitters reported ≥31 min of SOL and/or WASO. Daytime impairment in this subgroup of remitters was no different from that among individuals who met the diagnostic criteria at both baseline and follow-up (ie, chronic insomniacs). By contrast, follow-up impairment was significantly lower (F = 12.3; P < 0.01) among remitters whose sleep disturbance returned below empirically derived quantitative cutoffs (both SOL and WASO <31 min) than in chronic insomniacs.

This is the first study on the long-term course of insomnia based on the newly established DSM-5 criteria. A troubling implication of findings is that a majority of insomniacs stop meeting the diagnostic criteria despite continued sleep disturbance and impairment. "Remission" in these cases is attributable instead to tolerance of sleep symptoms. Incorporating quantitative criteria into current diagnoses may offer a more sensitive assay of treatment needs.