The Morningness-Eveningness Questionnaire (MEQ) and Munich ChronoType Questionnaire (MCTQ) are sometimes used to estimate circadian timing. However, it remains unclear if they can reflect a change in circadian timing after a light treatment. In this study, 31 participants (25-68 years) completed both questionnaires before and after a 13-28 day morning light treatment. The dim light melatonin onset (DLMO), a physiological marker of circadian timing, was also assessed in a subsample of 16 participants. The DLMO phase advanced on average by 47 minutes (p<0.001). The MEQ score increased by 1.8 points (p=0.046). The MSFsc measure derived from the MCTQ advanced by 8.7 minutes (p=0.17). The shift towards morningness observed in both questionnaires correlated with the phase advance observed in the DLMO (MEQ r=-0.46, p=0.036; MSFsc r=0.81, p<0.001). Results suggest that these circadian questionnaires can change in response to a light treatment, indicating they can reflect underlying changes in circadian timing.
Keywords: circadian; human; light; melatonin; sleep.