Circadian Phase and Phase Angle Disorders in Primary Insomnia.
Objectives
We aimed to identify the prevalence of circadian phase and phase angle abnormalities in patients with insomnia.


Methods
We conducted a cross-sectional, multicenter study at three sleep laboratories in the United States and Australia. Patients with insomnia and healthy control participants completed a sleep log for 7 days. Circadian phase was assessed from salivary dim light melatonin onset (DLMO) time during a 12-hour laboratory visit.


Results
Seventy-nine patients meeting the Research Diagnostic Criteria for Primary, Psychophysiological, Paradoxical, and/or Idiopathic Childhood Insomnia (46 females, 35.5 ± 12.3 years [M ± SD]) and 21 controls (14 females, 34.4 ± 11.8 years). As compared to controls, patients with insomnia tried to initiate sleep on average at the same clock time (24:17 ± 1:17 hours vs. 24:13 ± 1:30 hours, respectively; p = .84) but had a later average DLMO times (20:56 ± 1:55 hours, 18:17-01:21 vs. 22:02 ± 2:02 hours, 17:11-04:52, respectively; p = .04). Consequently, patients with insomnia slept at an earlier circadian phase than controls (phase angle, bedtime-DLMO 2:13 hours (± 1:43) vs. 3:10 hours (± 1:08), respectively; p = .008), of whom 10% tried to sleep at or before DLMO (compared to 0 controls), and 22% tried to sleep before or within 1 hour after DLMO (compared to 6% of controls).


Conclusions
A substantial proportion (10%-22%) of patients with insomnia initiate sleep at too early a circadian phase, implicating a circadian etiology for their insomnia. Outpatient circadian phase assessments should be considered to improve differential diagnoses in insomnia and to inform the development of appropriately timed circadian-based treatments.
['Flynn-Evans|Erin E|EE|', 'Shekleton|Julia A|JA|', 'Miller|Belinda|B|', 'Epstein|Lawrence J|LJ|', 'Kirsch|Douglas|D|', 'Brogna|Lauren A|LA|', 'Burke|Liza M|LM|', 'Bremer|Erin|E|', 'Murray|Jade M|JM|', 'Gehrman|Philip|P|', 'Rajaratnam|Shantha M W|SMW|', 'Lockley|Steven W|SW|']
D000328:Adult D001315:Australia D002648:Child D002940:Circadian Rhythm D003430:Cross-Sectional Studies D005260:Female D006801:Humans D008297:Male D008550:Melatonin D008875:Middle Aged D012463:Saliva D012890:Sleep D020178:Sleep Disorders, Circadian Rhythm D007319:Sleep Initiation and Maintenance Disorders D014481:United States
circadian phase angle insomnia melatonin DLMO 6-sulfatoxymelatonin circadian rhythms