Some standard measures of sleep-wake architecture showed changes with age in early childhood. There was no age-related change in mean total sleep following 13 h of prior wakefulness (A) or mean durations of NREM/REM sleep cycles (B), but NREM sleep episodes (C) increased with age; mean durations of REM sleep episodes showed no age-related change (D). Average changes between ages for each measure except total sleep were positive, suggesting trends for age-related increases (E, F, G, H, respectively). Bars indicate the 95 percent confidence interval of the means (A-D) and paired differences (E-H).