Late bedtime and body mass index gain in indigenous Australian children in the longitudinal study of indigenous children

Aim: To explore sleep patterns in indigenous Australian children and assess the role of sleep timing in longitudinal changes in body mass index (BMI). Methods: Latent profile analysis was conducted with the Australian Longitudinal Study of Indigenous Children (LSIC) cohort data (wave 5), to determine distinct patterns of bed and wake timing, taking account of weekday sleep duration, weekday and weekend bedtimes, and weekday wake times. Multilevel models with a random intercept were used to investigate the role of baseline sleep pattern in predicting longitudinal changes in BMI. Results: Baseline data for 1258 children (50.7% males), mean age 6.32 ± 1.52 years, indicated the presence of five classes of sleep patterns: early/long sleepers (4.5%), normative sleepers (25.5%), late sleepers (49.9%), consistent late sleepers (11.1%) and early risers (9%). Late sleeping was significantly associated with longitudinal gains in BMI. Compared with early sleepers, consistent late sleepers experienced 1.03 unit gain in BMI at follow-up (95% CI: 0.001-2.05, P =.05). Conclusion: This study underscores the importance of looking beyond sleep duration and highlights the positive outcomes of early bedtimes in children. As sleep timing is modifiable, this offers the opportunity for improvement in sleep and protecting against future weight gain in indigenous children.