Sleep Duration From Ages 1 to 10 Years: Variability and Stability in Comparison With Growth

Our goal was to describe the variability of sleep duration (time in bed per 24 hours) in healthy children from 1 to 10 years of age in comparison with growth measures. A total of 305 children were followed with structured sleep-related interviews and measurements of height and weight 12, 18, and 24 months after birth and then at annual intervals until 10 years of age. SD scores were calculated, and smooth curves were fitted by smoothing splines through the SD scores. The long-term variability channel within children (units SD score) was defined as the difference between the maximum and the minimum of the smooth curves and the short-term variability channel (units SD score) as the difference of the largest and the smallest deviations of the original SD scores from the smooth curve. Sleep duration remained within a long-term variability channel