Using actigraphy to assess chronotype: Simpler is better.

Actigraphy provides a unique method for objectively measuring sleep activity patterns, but confusion remains about how to use actigraphy data to determine chronotype. To determine the most suitable parameter, this study made a systematic comparison of actigraphy-derived parameters: the average midpoint of sleep of all record days (aMS-acti), cosine parameter (Bathyphase), and non-parametric parameter (L5-mid) in terms of the consistency with subjective chronotype parameters, test-retest reliability, and external validity. More importantly, we proposed multiple Munich Chronotype Questionnaire (MCTQ)-based actigraphy parameters: considering the difference between weekday (MSW-acti) with weekends (MSF-acti) and the sleep debt (MSFsc-acti). The study collected 5 days of actigraphy and scale data from 1,055 young adults, 138 of whom participated in the retest 2 years later. The results showed that, in terms of consistency with subjective chronotype, aMS-acti generally performed better than other actigraphy parameters. In addition, aMS-acti had the highest test-retest reliability and was more closely related to the Pittsburgh Sleep Quality Index (PSQI), Insomnia Severity Index (ISI), and Self-Rating Depression Scale (SDS). The results suggest that the simplest parameter (aMS-acti) is superior to traditional cosine and non-parametric parameters and MCTQ-derived parameters for short-term assessment of chronotype.