Dim light melatonin onset in normal adults and its relationship with sleep timing and diurnal preference

Abstract

Dim light melatonin onset (DLMO) is defined as the start of the melatonin production in the evening during dim light conditions and has become a reliable phase marker of the circadian clock. The aim of the study was to investigate DLMO and its association with sleep timing and diurnal preferences in healthy working adults during real-life conditions. Fourteen adults were investigated. A sleep diary was kept during the preceding week, but no fixed sleep–wake schedule was implemented. Diurnal preferences were measured with the Horne–Östberg Morningness–Eveningness Questionnaire. DLMO was defined as the time point when melatonin in saliva exceeded a threshold of 3 ng/L. Results showed that DLMO appeared in the expected time interval but was not significantly associated with sleep timing or diurnal preference. The results illustrate the complexity of monitoring sleep patterns in real-life settings.

Keywords:

• adults
• circadian rhythms
• diurnal preferences
• DLMO
• melatonin

Acknowledgement

This research was financially supported by Utvecklingsfonden at Uppsala University Hospital, Sweden.