How can social jetlag affect health?

Abstract

Our lives are governed by three clocks: the social clock that organizes our lives with others (local time), the biological clock that controls our physiology (circadian time) and the sun clock that defines natural light and darkness. The more misaligned these clocks are, the higher our odds of developing certain diseases. ‘Social jetlag’ quantifies the difference between local and circadian time.

Fig. 1. Average social jetlag across a lifetime.

Social jetlag, which can be calculated using the Munich ChronoType Questionnaire (MCTQ), is defined as the difference between the mid-point of sleep on workdays and on work-free days. Data are taken from the MCTQ database (n = 198,370) and were first published in Roenneberg et al. (2012). Except for the age groups of 10 and 11 years, standard errors of the mean are smaller than the symbols. The blue area indicates where social jetlag is smaller than 20 min, which appears to be the tolerable limit for people. The average age ± standard deviation of the study population in Bouman et al. is indicated by the dashed grey box.