Sleep behavior in an urban US sample of school-aged children.

OBJECTIVES: To describe sleep behavior of elementary school-aged children and to assess variations by age, sex, and ethnicity.

DESIGN, SETTING, AND PARTICIPANTS: Cross-sectional analysis of 755 (50% female, 35% ethnic minority) children 8 to 11 years old from a community-based sample of children participating in a cohort study. Sleep and health data were obtained from a child-completed 7-day sleep journal and a caregiver-completed health/sleep questionnaire.

MAIN OUTCOME MEASURE: Mean nightly sleep duration; bedtime 11 pm or later.

RESULTS: Mean (SD) sleep duration for all children was 9.63 (0.72) hours. Univariate results showed a statistically significant decrease in mean sleep duration associated with increasing age (P < .001) and male sex (P = .03). At all ages, minority boys slept significantly less than nonminority boys and girls and minority girls. The shortest covariate-adjusted mean sleep duration was observed among the oldest minority boys (9.28 [0.07] hours vs 9.43-9.85 hours in the other age, sex, and ethnicity subgroups). Forty-three percent of 10- to 11-year-old minority boys reported less than 9 hours nightly sleep vs 5% to 26% of the other age, sex, and ethnicity subgroups. After controlling for potential confounding, minority children were more likely than nonminority children to have a bedtime of 11 pm or later (odds ratio, 4.8; 95% confidence interval, 2.9-8.0).

CONCLUSIONS: A sizeable proportion of elementary schoolchildren sleep less than the recommended 9 hours. Across the age range, decreases in sleep time and, in ethnic minorities, increasingly delayed bedtimes suggest emerging sleep restriction in preadolescents. Observed ethnic differences in sleep behavior highlight the need for better understanding of the social and environmental influences encouraging these sleep patterns.