Sleep duration at 3 years of age can predict changes over time in body mass index (BMI) percentile, suggesting that obesity risk may be lower in children with longer sleep duration, according to study results published in Childhood Obesity.

Several studies have shown an association between poor sleep and obesity in young children, as short sleep duration can adversely affect metabolic regulation. However, other studies have had conflicting findings. In light of the mixed results on this association, the goal of the current study was to explore the influence of sleep trajectories in early childhood on obesity risk.

Of 372 healthy children aged 3 years enrolled in a prospective cohort study in Cincinnati, Ohio, 301 (51% boys) with complete data from ages 3 to 6 years were included in the analysis. Study visits occurred every 4 months.

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Average nighttime sleep duration, daytime nap duration, and 24-hour sleep duration (nighttime sleep plus daytime naps) were calculated using data from 3 days of actigraph use and sleep diaries. Latent growth curve models were estimated to test the average rates of change in sleep duration and BMI percentile over time, variability in change, and predictors of the initial status factor at age 3 years and the slope factor, or change over time.

At age 3 years, 21% of children had overweight or obesity, which increased to 32% of children at age 6 years. The average BMI percentile at age 3 years was 61.1%±27.0% and demonstrated a significant increase over time, reaching 66.6%±26.2% at age 6 years. On average, BMI percentile increased by 1.76% for each year of age (P <.001) and the changes in BMI percentile over time were not affected by levels of moderate/vigorous physical activity or television viewing.

Children had a similar bed and wake time across ages 3 to 6 years, with most having a bedtime after 9 PM. Total sleep duration was 11.2 hours at age 3 years and 10.5 hours at age 6 years, with nighttime sleep duration of 10.6 and 10.5 hours, respectively. The latent growth curve model showed there was a small but significant decrease in average sleep duration by 0.22 hours for each year of age (P <.001). Similar to BMI percentile, sleep duration was not affected by levels of moderate/vigorous physical activity or television viewing.

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Baseline sleep duration predicted the BMI percentile slope factor, as greater sleep duration at age 3 years was predictive of decreased BMI percentile over time (P =.012).

The researchers acknowledged that the study had potential limitations, as it was a secondary analysis from a larger study that was not originally designed to address the research question.

“Based on our findings, future interventions should be explored focusing on sleep behaviors before age 3 as a means of improving sleep and reducing obesity risk in children,” concluded the researchers.

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Kaar JL, Schmiege SJ, Kalkwarf HJ, Woo JG, Daniels SR, Simon SL. Longitudinal assessment of sleep trajectories during early childhood and their association with obesity. Child Obes. 2020;16(3):211-217.