An assessment of chronotype and social jetlag among Filipinos

Abstract

Chronotype is a measure of an individual's timing of sleep and wakefulness. It describes the relationship between an external time and a person's internal biological time. The chronotype has been used to characterize human circadian trait. Differences in chronotypes are believed to be related to genetic variation, location, geographic and cultural factors. Determination of chronotype using quantitative approaches has been done in Europe for more than a decade now through the Munich Chronotype Questionnaire (MCTQ). In this approach, the chronotype is quantified by the midpoint time between the start and end of sleep during free days, corrected for sleep duration on work days. The calculated time classifies whether an individual has an early or late chronotype. In the Philippines, there is no existing data for chronotypes as well as social jetlag - the discrepancy between an individual's internal time and social clock. In this study, we provide a quantitative description of chronotypes and social jetlag among Filipinos. We present preliminary results based on the 895 non-shift worker respondents of the PhilMCTQ, a language variant of the MCTQ for the Philippine population. Using this set of data, we determined the association of chronotype and social jetlag against certain factors, i.e., age, gender, self- assessed exposure to natural light, type of location (whether living in the urban or rural area), travel time to/from work, sleep duration, and body mass index. Observations concerning the relationship of chronotype and gender, age and social jetlag that have been previously reported in other populations are also seen in our data. Increased social jetlag has been observed among people with late chronotypes among our respondents. There were also some differences in chronotypes between genders, age groups, dwelling locations and consumers of stimulants (i.e., beer, liquor and cigarettes). Both Metro City and Non-Metro City residents similarly experience social jetlag. The data show that as commuting time becomes longer, social jetlag slightly increases. Differences in social jetlag have been observed between age groups and certain stimulants (e.g., smoking, coffee drinking) have been shown to be associated with social jetlag. Other factors such as gender, dwelling location, time spent outdoors and body mass index did not show sufficient evidence of association or correlation with social jetlag among the study participants.