Associations of sleep characteristics with cognitive and gross motor development in toddlers.

OBJECTIVE: To examine cross-sectional associations of sleep characteristics (duration, consolidation, timing, variability) with cognitive and gross motor development in toddlers. METHODS: Participants were 205 toddlers (19.6 ± 4.3 months) from the GET-UP! STUDY: Nap/nighttime sleep onset and offset were measured using an accelerometer and used to calculate nap/nighttime sleep duration. Total sleep duration was calculated and classified as meeting or not meeting the sleep recommendation of the Australian 24-Hour Movement Guidelines (11-14 h/d). Nighttime sleep ratio (ie, nighttime sleep duration: total sleep duration), indicative of consolidation, was expressed as a percent value. Nighttime sleep midpoint (ie, the midpoint between nighttime sleep onset and offset), indicating the lateness of sleep schedules, was converted to a decimal hour. For sleep variability, the intraindividual standard deviation of nighttime sleep duration and nighttime sleep midpoint was calculated, respectively. Cognitive development (Bayley Scales of Infant and Toddler Development-III) and specific domains of gross motor development (Peabody Developmental Motor Scales, 2nd edition) were measured. RESULTS: Shorter nap duration (B = -0.87, 95%CI: -1.71, -0.02) and higher nighttime sleep ratio (B = 0.13, 95% CI: 0.02, 0.24) were associated with better cognitive development. Regarding gross motor development, positive associations were found for nighttime sleep duration (object manipulation: B = 0.26, 95% CI: 0.01, 0.51; gross motor quotient: B = 1.21, 95% CI: 0.04, 2.38) and total sleep duration (object manipulation: B = 0.28, 95% CI: 0.03, 0.52); negative associations were found for nighttime sleep midpoint (stationary: B = -0.31; 95% CI: -0.58, -0.06) and nighttime sleep duration variability (stationary: B = -0.32, 95% CI: -0.64, -0.004). CONCLUSIONS: In toddlers, more consolidated sleep may be an indicator of better cognitive development. Promoting longer and more consistent nighttime sleep duration, as well as an earlier nighttime sleep schedule, may facilitate gross motor development. However, our findings for the associations of sleep characteristics with cognitive and gross motor development need to be confirmed in prospective studies.