Associations of excessive internet use, sleep duration and physical activity with school absences: a cross-sectional, population-based study of adolescents in years 8 and 9.

Background: Internet use has increased and sleep and physical activity (PA) have decreased in recent years among adolescents. Besides sleep and PA, another determinant of future health for adolescents is education. Our aim was to evaluate the associations of excessive internet use (EIU), short sleep duration and low PA with both unexcused absences and medical absences during lower secondary school.