Disrupted sleep maintenance is associated with altered circadian phase and phase angle in community-dwelling adults

We aimed to compare the sleep onset, dim light melatonin onset (DLMO) and phase angle (PA) between sleep onset and DLMO of insomnia patients with those of controls, and to examine the difference in these parameters in relation to objective sleep quality.

Participants were recruited from three Public Health Centers in Korea. Actigraphy recordings were conducted for seven days. Five hourly saliva samples were obtained from three hours prior to sleep onset. A total of 48 controls and 64 insomnia patients were analyzed. Nocturnal sleep parameters, DLMO, and PA were compared between the controls and insomnia patients, and between the controls and patients with difficulty in maintaining sleep (DMS). These sleep and circadian parameters were compared among the subgroups divided by wake after sleep onset (WASO) amount.

There were no significant differences in sleep parameters between the control and insomnia groups, and between the controls and DMS subgroup. The sleep onset, DLMO, and PA of the insomnia group or those of DMS subgroup were not different from those of controls. There were significant differences in the sleep onset and DLMO (p < 0.05) among mild, moderate, and severe WASO groups. A regression analysis revealed the earlier DLMO and shorter PA predicted the severity of WASO (p < 0.0001) in total participants.

Insomnia patients exhibited no difference in their sleep timing and melatonin rhythm compared to controls. However, these circadian parameters varied depending on the severity of WASO, and advanced melatonin phase and its shortened phase angle were associated with worsening of sleep maintenance.