A survey on social jetlag in Japan: a nationwide, cross-sectional internet survey

Yoko Komada,Isa Okajima,Yuichi Inoue,Shingo Kitamura

doi:10.1007/s41105-019-00229-w

Abstract

Misalignment between an individual’s circadian phase and his/her environment due to social imposition is called social jetlag (SJL). SJL has emerged as a public health concern, as it contributes to an unhealthy lifestyle and adverse health outcomes. This study aimed to elucidate the percentage of SJL in a large Japanese population using the Japanese version of the Munich ChronoType Questionnaire (MCTQ). A total of 10,000 participants responded to a web-based cross-sectional survey, and the final sample comprised 3708 participants (60.1% male; average age 45.1 [SD 13.4] years). SJL was measured by subtracting each participant’s midpoint of sleep on workdays from their midpoint of sleep on free days. The average [SD] absolute SJL (SJLabs) value was 0.91 [0.89] hours, and the percentage of participants with SLJabs of more than 1 h was 40.1%. Our data also showed that SJLabs becomes progressively smaller with advancing age. A considerable number of participants of our Japanese population showed differences in sleep behavior between workdays and free days. Young people in particular commonly oversleep on free days to compensate for the sleep debt accumulated over the workweek because of their late chronotype.

Highlights

The endogenous circadian timing system is responsible for the maintenance and coherence of physiological processes and their synchronization with environmental light–dark cycles [1, 2]
social jetlag (SJL) is a measure of the discrepancy in sleep timings between our workdays and free days [6, 7] and was so named owing to the similarity to travel-induced jetlag caused by taking a flight to the west on Friday evening and a return flight on Monday morning
A recent study indicated that SJL is negatively associated with serum brain-derived neurotrophic factor (BDNF) levels, which plays an important role in neuronal maintenance, plasticity, and neurogenesis [14]

Summary

Introduction

The endogenous circadian timing system is responsible for the maintenance and coherence of physiological processes and their synchronization with environmental light–dark cycles [1, 2]. SJL has been related to unhealthy behaviors such as smoking [6] or physical inactivity [8] and has been suggested as a risk factor for obesity [9], metabolic dysfunction that may lead to a predisposition to diabetes, atherosclerotic cardiovascular disease [10,11,12], and depression [13]. It has emerged as a public health concern. A recent study indicated that SJL is negatively associated with serum brain-derived neurotrophic factor (BDNF) levels, which plays an important role in neuronal maintenance, plasticity, and neurogenesis [14]

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