Measuring sleep in young children and their mothers: Identifying actigraphic sleep composites.

The present study considered multiple aspects of sleep in a community sample of young children (at ages 30, 36, and 42 months) and their mothers, using both diaries and actigraphy. Through principal components analysis, 17 of 20 commonly used actigraphy variables were reduced to four main components whose variables formed composites of: Activity, night-to-night Variability, Timing, and Duration. Sleep latency and daytime sleep variables remained separate from the composites. The same components were identified at each age, and for both children and mothers. Furthermore, the sleep composites derived from the components showed greater cross-age stability than individual actigraphy variables. Finally, child and mother sleep composites were related concurrently and longitudinally. These findings demonstrate a systematic and efficient way of summarizing child and mother sleep with actigraphy variables.