Shifting chronotypes: Sleep patterns among adolescents living in industrial and pre-industrial environments

Abstract

Using biosocial, cross-cultural, anthropological perspectives, this research compares sleep patterns of adolescents (aged 11-16) in one industrial society and two non-industrial societies in Mexico to help unravel evolutionary and cultural aspects shaping contemporary adolescent sleep. Specifically, this study examines whether the shift in the adolescent sleep-wake cycle reported among industrialized populations is replicated in non-industrialized societies with little access to electronic and/or electrical devices and whether sleep sufficiency is greater in non-industrial settings.

Adolescents (n=145) wore Motionlogger Micro Watch units for 24 hours over ten days and completed sleep diaries to obtain sleep measurements of sleep timing and duration. Data about the participant’s sleep environment were assembled through semi-structured interviews and ethnographic observation. Information from the Pubertal Developmental Scale was used to discuss changes in adolescent sleep. The between-population variation in sleep measures was investigated by fitting different types of three-level models.

Pubertal development was associated with a delay in sleep timing during non-school days, and this was significant in all but one of the non-industrial sites. Sexual maturation was also associated with a shorter sleep duration during school nights, but no such association was identified for adolescents in the industrial site. Short sleep quotas were as prevalent in non-industrial-site teenagers as in their industrial-site counterparts. Sleep timing and duration were more responsive to natural light-dark cycles and social sleep in non-industrial settings.

Results provide novel evidence of flexible sleep-wake patterns in adolescents and highlight the influence of social activities on the expression of human sleep behaviour. Adolescent circadian plasticity might result from life-history trade-offs related to the switchover to future investment in reproduction. Circadian plasticity might have been advantageous in ancestral human environments, benefitting individual and group fitness. Any sleep interventions to improve contemporary adolescent wellbeing should address individual and community needs to develop more equitable and effective health policies and practices.