Association of nighttime sleep with behaviors in Japanese early childhood.

Abstract

Preschool children in Asian countries, including Japan, sleep for a shorter duration at night than those in Europe and the USA. We examined the effects of the nighttime sleep duration on behavioral development in early childhood in Japan. We used data from a large Japanese nationwide, population-based, longitudinal survey that began in 2001. We restricted the study participants to children born after 37 gestational weeks, with a birth weight ≥ 2500 g and singleton births (n=41 890). The nighttime sleep duration was examined at 2.5 years old. Responses to survey questions regarding age-appropriate behavior at 5.5 years old were used as indicators of behavioral development. We conducted logistic regression analyses with adjustment for confounding factors, with ≥11h of nighttime sleep as the reference group. The odds ratios for children who had ≤9 h of nighttime sleep, which was associated with being unable to listen with fidgeting and being unable to remain patient, were 1.26 (95% confidence interval, 1.14-1.39) and 1.27 (1.16-1.38), respectively. Children who had an irregular nighttime sleep duration were associated with age-appropriate behavioral inabilities. These results were similar in children who usually and sometimes took naps to those before stratification by the frequency of napping. A short nighttime sleep duration especially affects hyperactivity and impulsivity. An irregular nighttime sleep duration increases the inability to perform overall age-appropriate behaviors more than a short sleep duration. Ensuring a regular and sufficient nighttime sleep duration in early childhood is important for healthy behavioral development.