Intraindividual variability in sleep patterns and behavioral problems among preschool children: The role of bedtime and total sleep time variability

Sleep stability is critical for early childhood development, yet many children experience variability in sleep patterns that may affect behavioral health. This study examines the impact of intra-individual variability (IIV) in sleep on behavioral issues in young children, independent of average nighttime sleep duration reported via BISQ. A sample of 306 children aged 1.5 to 5 years was recruited through the Health and Social Welfare Division, A City. Caregivers reported sleep patterns using daily activity logs, and behavioral problems were assessed using the Child Behavior Checklist 1 1/2 -5. Main sleep measures included total sleep time and weekly standard deviations of bedtime, wake time, and total sleep time, reflecting sleep IIV. Logistic regression analyses adjusted for confounding factors (e.g. child age, birth order, maternal age at birth) indicated that higher IIV in bedtime was significantly associated with increased internalizing problems, while greater IIV in total sleep time was linked to externalizing problems. Both indicators of IIV were also associated with overall behavioral problems, independent of average nighttime sleep duration. These findings underscore the relevance of consistent sleep-wake rhythms for emotional and behavioral stability in early childhood and indicate that addressing sleep IIV could support efforts to foster healthier behavioral development.