Estimating sleep patterns with activity monitoring in children and adolescents: How many nights are necessary for reliable measures?

Study Objectives: This study provides estimates of reliability for aggregat ed values from 1 to 7 recording nights for five commonly used actigraphic m easures of sleep patterns, reliability as a function of night type (weeknig ht or weekend night), and stability of measures over several months, Design and Setting: Data are from three studies that obtained 7 nights of a ctigraph data (using Mini Motionlogger actigraphs and associated validated algorithms [ASA]) on children and adolescents living at home on self-select ed sleep-wake schedules, Participants: Participants were 169 children aged 12-60 months, and 55 adol escents aged 11-16 years. Measurements and Results: Up to 28% of weekly recordings may be unacceptabl e for analysis in young participants because of illness, technical problems and participant noncompliance; studies aiming to collect 5 nights of actig raph data should record for at least 1 full week. Reliability estimates for values aggregated over any 5 nights were adequate (greater than or equal t o.70) for sleep start time, wake minutes, and sleep efficiency. Measures of sleep minutes and sleep period were less reliable and may require 7 or mor e nights for estimates of stable individual differences. Reliability for 1- or 2-night aggregates were poor for ail measures. We found significant and high correlations between summer and fall session measures for all five Va riables when weekend nights were included. Conclusions: Five or more nights of usable recordings are required to obtai n reliable actigraph measures of sleep for children and adolescents.