Associations of Morning-evening Preference with Morning Gastric Motility and Vital Parameters among Female High School Students Living in a Dormitory

Abstract

Objective: A previous study on female students with evening preference showed an attenuated activity of the cardiac autonomic nervous system (ANS) in morning and a fluctuated gastric motility caused by mealtime. We further examined the association of morning-evening (ME) preference with morning gastric motility and vital parameters in female high school students who have the same mealtime, as they live in a school dormitory. Methods: Forty-one students were measured in terms of blood pressure, eardrum temperatures, electrocardiography (ECG), and electrogastrography for 10 min before breakfast at temporally setting measurement room in the dormitory. Cardiac ANS activity and averaged heart rate (HR) were calculated from the ECG. To evaluate fasting gastric motility (occurring 3 cycles/min), an action potential was derived from electrodes placed on the abdomen. Thereafter, power and peak frequency was analyzed by a power spectral analysis method. According to total ME scores, calculated from 10 questions (1-5 points, respectively), students were divided into morning (≥ 28.5 [mean] points) or evening preference groups (< 28.5 points) and the parameters were compared between the groups. Results: As compared to the morning preference group, the evening preference group showed 1) a significantly delayed wake-up time on both weekdays and weekends, 2) a significantly higher HR, and 3) a significantly higher frequency of gastric motility without any differences in gastric contraction power. Conclusion: Female high school students with evening preference showed a high HR after awakening without a diminished gastric motility, possibly suggesting the occurrence of food anticipated activity induced by regular mealtime.