Appendix A.

Actigraphy variables included in composites

Sleep Composite	Variable Descriptions
Sleep Duration	Average sleep period (minutes)
	Average duration of time in bed (minutes)
	Average minutes asleep in bed
Sleep Timing	Average time of midsleep (HH:MM in 24-hour time)
	Average time of sleep onset (HH:MM in 24-hour time)
	Average bedtime (HH:MM in 24-hour time)*
Sleep Variability	SD of time of sleep onset
	SD of duration in bed
	SD of duration of sleep period
	SD of time of midsleep
	SD of bedtime*
	SD of minutes asleep in bed
Sleep Activity	Average time (minutes) awake after sleep onset
	SD of average minute to minute activity levels
	Average number of awakenings (lasting 5 minutes or more)
	Average duration (minutes) of longest wake episode (after sleep onset)

Note.

^*bedtime variable was based on mother report of time in bed on the daily diary