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Assessment of Child Anthropometry in a Large Epidemiologic Study
Published on: February 2, 2017
Bedtime, body mass index and obesity risk in preschool-aged children
Melyssa Roy1, Jillian J Haszard2, Jennifer S Savage3
1Department of Medicine, University of Otago, Dunedin, New Zealand.
Insights
Bedtime alone is inconsistently linked to childhood obesity. However, longer sleep duration, regardless of bedtime, was associated with lower obesity risk in young children.
Area of Science:
- Pediatric Health
- Sleep Science
- Obesity Research
Background:
- Sleep duration is a known risk factor for childhood obesity.
- Limited research exists on the impact of specific sleep aspects, like bedtime, on obesity risk in young children.
Purpose of the Study:
- To investigate the association between bedtime and body mass index (BMI) z-score or obesity risk in children aged 2 to 5 years.
- To determine if these associations are independent of total sleep duration.
Main Methods:
- Utilized data from three early life obesity prevention trials and one longitudinal cohort study, including 1642 children.
- Assessed bedtime via questionnaire and BMI through clinical measurements between ages 2 and 5 years.
- Employed adjusted regression models and a discrete mixture model to analyze BMI z-score, obesity risk, and sleep trajectory groups.
Main Results:
- Bedtime showed inconsistent associations with BMI z-score.
- Later bedtimes were linked to increased obesity odds at ages 3 and 5, but this effect diminished after adjusting for sleep duration.
- Longer nocturnal sleep duration at age 2 and longer 24-hour sleep duration at age 3 (in girls) were associated with lower obesity odds.
Conclusions:
- The timing of bedtime appears to have an inconsistent relationship with obesity in young children.
- This association may be mediated by its influence on overall sleep duration, with longer sleep being protective against obesity.
Background:
Although sleep duration is a risk factor for obesity in young children, less is known about other aspects of sleep health, including bedtime, on obesity risk.
Objective:
To determine whether bedtime is associated with body mass index (BMI) z-score or obesity risk in children ages 2 to 5 years, and to determine if associations are independent of sleep duration.
Methods:
Cohort analyses were undertaken using three early life obesity prevention trials (POI, INSIGHT, Healthy Beginnings) and a longitudinal cohort study (HOME). Bedtime was assessed by questionnaire and BMI through clinical measurement between 2 and 5 years in 1642 children. Adjusted regression models examined whether BMI z-score and obesity (BMI z-score ≥ 2) were associated with bedtime, nocturnal sleep time and 24-hour sleep time. A discrete mixture model categorized children into bedtime trajectory groups across time points.
Results:
Bedtime was inconsistently associated with BMI z-score. Although each hour later of bedtime was associated with greater odds of obesity at ages 3 (OR; 95% CI: 1.05; 1.003, 1.10) and 5 (1.35; 1.08, 1.69) years, odds were attenuated after adjustment for nocturnal or 24-hour sleep time. Longer nocturnal sleep duration at 2 years was associated with lower odds of obesity (OR 0.90; 0.86, 0.94), as was longer 24-hour sleep duration at 3 years in girls (0.70; 0.62, 0.78). BMI z-score and odds of obesity were not significantly different between 'early to bed' and 'late to bed' trajectory groups.
Conclusions:
Timing of bedtime appears inconsistently related to obesity in young children, possibly via influencing overall sleep duration.
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