Circadian Phase and Phase Angle Disorders in Primary Insomnia.
Level 4 - case-series / case-control
Cross-sectional case-control study
PubMed 29029340 · doi:10.1093/sleep/zsx163
What was done
A cross-sectional multicenter study evaluated circadian timing across three sleep laboratories in the United States and Australia. Participants included 79 patients meeting diagnostic criteria for primary, psychophysiological, paradoxical, or idiopathic childhood insomnia (mean age 35.5 ± 12.3 years, 46 females) and 21 healthy controls (mean age 34.4 ± 11.8 years, 14 females). All participants completed a 7-day sleep log, and their circadian phase was determined via salivary dim light melatonin onset (DLMO) during a 12-hour laboratory session.
What was found
Patients with insomnia attempted sleep at a similar clock time to controls (24:17 ± 1:17 vs. 24:13 ± 1:30 hours; p = .84), but exhibited later average DLMO timing (22:02 ± 2:02 vs. 20:56 ± 1:55 hours; p = .04). Consequently, insomnia patients had a significantly shorter phase angle between DLMO and bedtime than controls (2:13 ± 1:43 vs. 3:10 ± 1:08 hours; p = .008). Ten percent of insomnia patients attempted sleep at or before DLMO (compared to 0% in controls), and 22% attempted sleep within 1 hour after DLMO (compared to 6% in controls).
Why it matters
The findings indicate that a subset of primary insomnia cases involves an underlying circadian phase-angle misalignment rather than purely non-circadian sleep disturbances, suggesting targeted circadian interventions may benefit these patients.
Limits
The control group was small (n = 21) compared to the insomnia cohort (n = 79). The cross-sectional design cannot establish causality between phase-angle abnormalities and insomnia symptoms. Circadian phase was assessed during a single 12-hour laboratory visit, and clinical outcomes following circadian treatments were not evaluated.
Cited by
- supports Melatonin levels typically begin to rise 2 to 3 hours before habitual sleep time.