Association of social jet lag and chronotype with academic performance among dental students

Objectives: Social jet lag （SJL） is a recurrent state of jet lag caused by the discrepancy in a person’s sleep pattern between workdays and holidays due to work and social schedules. It has been reported that a larger SJL is significantly correlated with lower academic performance. The present study included fifth-year dental students who attended a remote lecture course for two months prior to starting clinical practice. We deduced that it was difficult for them to maintain their daily rhythm during the two months of remote learning. We focused on the chronotype and SJL of those students who had to make a switch to a morning-oriented daily rhythm and investigated the association with academic performance. <br>Methods: The Japanese version of the Morningness-Eveningness Questionnaire （MEQ）, which has 19 items, was distributed to the students and collected on the spot after they completed it—they were asked to indicate their sleep start and end times on the days with lectures and practical work, and on holidays. Based on their MEQ score, they were classified into three chronotypes: morning type, intermediate type, and night type. The median time of sleep （midpoint of sleep on workdays ［MSW］ and midpoint of sleep on free days ［MSF］） was calculated by adding the sleep start and end times and dividing by two. SJL was calculated by subtracting MSW from MSF. Grade Point Average （GPA） was analyzed using the total score of the achievement test, which was held every three weeks and 12 times throughout the year. <br>Results: In GPA, there was no significant difference between genders, but there was a significant difference （p＜0.05） between the students who had repeated grades and the students who had not. Among the students who had repeated grades, there was a significant negative correlation （rs＝−0.462, p＜0.05） between GPA and SJL. <br>Conclusions: We found that there was a significant negative correlation between SJL and academic performance among dental students who had been retained. This indicates that irregular circadian rhythms may affect dental students’ academic performance.