Associations between objectively measured nighttime sleep duration, sleep timing, and sleep quality and body composition in toddlers in the Guelph Family Health Study

The prevalence of child obesity is a worldwide public health concern. Good sleep quality is associated with reduced adiposity in older children and adults. More research is needed in younger children to help mitigate risk of obesity. In addition, we aimed to address limitations found in previous studies such as relying on subjective measures, or only including one parameter of sleep, using only one body composition parameter, and/or not adjusting for relevant covariates. This cross-sectional study examined baseline data from 48 toddlers aged 1 to <3 years enrolled in the Guelph Family Health Study. Nighttime sleep duration (total sleep time; TST), sleep timing (sleep onset and offset time), and sleep quality (wake after sleep onset; WASO) were measured using 24 h accelerometry for 7 consecutive days. Height, body weight, and waist circumference were measured, and BMI z-scores and waist-to-height ratios were calculated. Percent fat mass and fat mass index were calculated using bioelectrical impedance analysis. Linear regression models were used to estimate associations between sleep parameters and body composition outcomes, with adjustments for relevant covariates (age, sex, household income, screen time, energy intake, physical activity, household stress). Nighttime sleep onset time was positively associated with waist-to-height ratio (<(beta)over cap> = 0.004, p = 0.04). Sleep offset time was negatively associated with BMI z-score ((beta) over cap= -0.48, p = 0.02). TST and WASO were not associated with any body composition outcome. Building healthy sleep habits may prevent childhood obesity; longitudinal research in a larger sample is warranted. This study was registered on ClinicalTrials.gov (NCT02939261).