The relationships between sex, age, geography and time in bed in adolescents: a meta-analysis of data from 23 countries.

OBJECTIVES

To quantify the relationships between age, sex and country of residence and sleep time (time in bed) in young people aged 9-18 years.

METHODS

Thirty studies of sleep patterns in healthy adolescents from the last 30 years in 20 countries were reviewed. Monte Carlo simulation generated pseudo-data where only summary statistics were available. Raw and pseudo-data were combined, generating a total of 92,977 data points. A mixed model, clustering on countries, analysed data for school and non-school days separately.

RESULTS

Sleep time varied with sex, age and geographical region. School day sleep differed slightly between boys and girls, girls sleeping 11 min/night more than boys (p = 0.003). On non-school days, girls slept 29 min more each day (p = 0.003). Sleep time declined with age, - 14 min/day per year of age (school days), and seven min/night per year of age (non-school days). Large differences between countries, showed adolescents from Asian countries sleeping 40-60 min less each night than Americans, and 60-120 min less than Europeans.

CONCLUSION

Sex, age, geographical region and day type interact and predict sleep patterns in adolescents. One consistent trend is the increasing gap between sleep on school days and non-school days as adolescents get older.