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ABSTRACT
The measurement of chronotype and circadian rhythms in polysomnography (PSG) studies is unresolved as no validated PSG markers have been published before. Data suggest that overnight changes in sleep spindle frequency (SSF) are due to a time-of-day effect, the nadir reflecting the middle of the biological night. In this study, we tested the nadir of sleep spindle frequency (NSSF) as a phase angle estimate of the circadian rhythm. The associations between NSSF, Munich Chronotype Questionnaire (MCTQ) and actigraphy-derived sleep midpoints were analysed in a healthy young adult sample (N = 31; 16 females). MCTQ sleep midpoints on workdays, furthermore all actigraphy-derived sleep midpoint metrics and the least active 5 hours were consistent with the individual differences in NSSF, highlighting the potential use of NSSF as a chronotype indicator. Although further validation is needed, these results could open new horizons in the role of PSG recordings in circadian rhythm research
Disclosure statement
No potential conflict of interest was reported by the author(s).
Author contribution
C. G.H. designed and conceptualized the study, performed analyses, collected the data, interpreted the results and wrote the paper. R. B. designed and conceptualized the study, interpreted the results and wrote the paper. Both authors revised and approved the final version and agree to be accountable for all aspects of the work.
Data availability statement
The dataset analysed during the current study is available here: OSF repository.