In 128 participants diagnosed with insomnia disorder, a longer phase angle between and sleep onset time was linked to a mean difference of 43.21 minutes in sleep latency.
Dim-light melatonin onset (DLMO) timing is associated with sleep timing in individuals with insomnia.
There are positive correlations between DLMO timing and sleep onset time, with correlation coefficients ranging from r = 0.27 to 0.37.
A longer phase angle (greater than 3 hours) between DLMO and sleep onset time is linked to longer sleep latencies and shorter sleep durations.
Participants with a phase angle less than 2 hours experienced shorter sleep latencies and longer sleep durations compared to those with longer phase angles.
No consistent associations were found between other phase angles (DLMO and mid-sleep, wake time) and sleep continuity.
Simplified
Circadian rhythmicity plays a crucial role in regulating sleep timing and continuity, but it may be altered in people with insomnia. This study tested whether (DLMO) timing is associated with sleep difficulties in insomnia. In total, 128 people diagnosed with insomnia disorder were recruited. Participants completed daily sleep diaries and wore an actigraph for up to 14 days before the laboratory visit to estimate mean sleep continuity (e.g., sleep latency, sleep duration) and sleep timing (sleep onset time and wake time from diaries, bedtime from diaries and actigraphy). After a sleep study, participants underwent salivary melatonin collection to estimate DLMO on the following night. Regressions and analyses of variances on tertile groups tested associations between DLMO (clock times and phase angle differences between DLMO and sleep timing) and sleep continuity and timing. There were associations between DLMO and sleep timing, r = 0.27-0.37, but not with sleep continuity. The phase angle between sleep onset time and DLMO was associated with sleep latency, sleep duration, and sleep efficiency, r = -0.32 to 0.41. Participants with a longer phase angle between DLMO and sleep onset time (> 3 h; i.e., greater delays) had longer sleep latencies (Mean diff = 43.21 min, SE = 12.99, p = 0.004) and shorter sleep durations (Mean diff = -65.66 min, SE = 20.75, p = 0.006) than participants with a shorter phase angle (< 2 h). Other phase angles (DLMO and mid-sleep, wake time) were not consistently associated with sleep continuity. Melatonin onset timing is associated with sleep timing in insomnia disorder. Larger phase angle differences between sleep onset and DLMO are linked to poorer sleep continuity. These findings highlight the importance of considering circadian alignment and its impact on sleep in understanding the pathophysiology of insomnia and in developing targeted treatment interventions. (s) (s)
Key numbers
43.21 min
Sleep Latency Increase
Mean difference in sleep latency for > 3 h subgroup vs. < 2 h subgroup.
-65.66 min
Sleep Duration Decrease
Mean difference in sleep duration for > 3 h subgroup vs. < 2 h subgroup.
21:11 hours
Timing Mean
Mean timing reported in the study.
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H.S. reports in‐kind research support from Retime Pty Ltd., Compumedics Ltd., and Withings Ltd.; and research grants from the American Academy of Sleep Medicine Foundation and Flinders University. L.L. reports in‐kind research support, patents commercialized by Retime Pty. Ltd. He is a shareholder of the company. C.J.G. was an original inventor of SleepFix and has free access for use in research. All other authors have no relevant competing interests to report.
