Sleep duration and body mass index in 0-7-year olds.

Objectives: To determine in children aged 0-7 years (1) cross-sectional relationships between body mass index (BMI) and sleep duration, and whether (2) sleep duration predicts later BMI and/or (3) BMI predicts later sleep duration.

Design: Longitudinal Study of Australian Children, Waves 1 and 2.

Participants: Infants aged 0-1 years (Wave 1), followed at age 2-3 years (Wave 2); children aged 4-5 years (Wave 1), followed at age 6-7 years (Wave 2).

Main Outcome Measures: BMI, sleep duration by time-use diary, parent-reported sleep problems (none/mild vs moderate/severe).

Analyses: Cross-sectional, ANOVA (sleep duration) and χ(2) (sleep problems); longitudinal, linear regression.

Results: 3857 (76%) infants and 3844 (77%) children had BMI and sleep data. At every wave, approximately 15% and 5% of children were overweight and obese, respectively. Obesity was not associated with sleep duration at 0-1, 2-3 or 4-5 years, though obese 6-7-year olds slept approximately 30 min less (p<0.001). Sleep problems were similar across BMI categories at all ages. Wave 1 sleep duration did not predict Wave 2 BMI, nor did Wave 1 BMI predict Wave 2 sleep duration.

Conclusions: In these large child population cohorts, sleep duration did not predict obesity up to age 6-7 years. Current trials of sleep interventions to prevent or manage obesity in young children may be premature.