Later high school start times associated with longer actigraphic sleep duration in adolescents

Abstract

Study Objectives High school start times (SSTs) directly impact adolescents' sleep timing and duration. This study investigated the associations between SSTs and actigraphically-measured 24-hour sleep duration, sleep onset, sleep offset and sleep quality. Methods This study included 383 adolescents (M age = 15.5, SD age = 0.6 years) participating in the age 15 wave of the Fragile Families & Child Wellbeing Study, a national birth cohort study sampling from 20 large US cities. Multilevel models used daily observations (N = 1116 school days, M days = 2.9, SD days = 1.4 per adolescent) of sleep and SSTs from concordant daily diary and actigraphy. Results A diverse range of SSTs were included in our analyses (M SST = 08:08, SD SST = 39 minutes, Range SST = 06:00-11:05), and are presented in the following categories for ease of interpretation: before 07:30, 07:30-07:59, 08:00-08:29, and 08:30 or later. Adolescents starting school at 08:30 or later exhibited significantly longer actigraphically-assessed 24-hour sleep duration (by 21-34 minutes, p