Table 4.

Proposed Variable Definitions for Actigraphy When Used in Pediatric Research

Reported Variables
Bedtime	Clock time attempted to fall asleep as indicated by either sleep diary or event marker
Wake Time	Clock time of final awakening in the morning as indicated by either sleep diary or event marker
Sleep Opportunity (Time in Bed)	Time between Bedtime and Wake Time (reported in minutes or hours)
Actigraphy Variables
Sleep Onset	Clock time for first of a predetermined number of consecutive minutes of sleep following reported Bedtime
Sleep Offset	Clock time for last of a predetermined number of consecutive minutes of sleep prior to reported Wake Time
Sleep Period	Duration between Sleep Onset and Sleep Offset (reported in minutes or hours)
Total Sleep Time (TST)	Duration of sleep in Sleep Period (reported in minutes or hours)
Sleep Onset Latency	Time between Bedtime and Sleep Onset (reported in minutes)
Wake After Sleep Onset (WASO)	Number of minutes scored as wake during Sleep Period
Sleep Efficiency	(TST ÷ time in bed) × 100 (expressed as percent) [Alternatively: (TST ÷ Sleep Period) × 100 (expressed as percent)]
Night Waking	Predetermined number of minutes of wake (e.g., 5 minutes) preceeded and followed by predetermined number of minutes of sleep (e.g., 15 minutes)
Night Waking Frequency	Number of Night Wakings
Night Waking Duration	Sum or average of minutes scored as Night Waking
24 Hour Sleep Duration	Amount of sleep in 24 hour period (reported in minutes or hours)
Less Commonly Reported
Midpoint	Clock time halfway between Sleep Onset and Sleep Offset
Naps (Frequency and/or Duration)	Scoring rules similar to “Night Waking” required to define “Nap” in terms of the predetermined number of minutes asleep preceeded and followed by predetermined number of minutes of wake. Then can define Nap Frequency and Nap Duration