Weighing the Causal Evidence That Associates Short Sleep Duration With Obesity

Accuracy of parent-reported sleep duration among adolescents assessed using accelerometry

IMPACT

Parent-reported children's sleep duration is a primary outcome measure in population-level studies, and is the primary driver of pharmacotherapy such as melatonin. Accelerometry using the Fitbit suggests that few adolescents sleep for the optimal 9-12 h as recommended by the American Academy of Sleep Medicine, and most parent reports grossly overestimate average nightly sleep duration. Parent reports of adolescent sleep duration are unreliable, and quantitative assessment of children's sleep duration should be considered when a significant step such as pharmacotherapy is undertaken for sleep.

Weekday time in bed and obesity risk in adolescence

INTRODUCTION

Sleep curtailment is associated with obesity in children, but few studies have investigated this relationship in a longitudinal sample of adolescents. The aim of the present study was to examine the longitudinal association between weekday time in bed (TIB) at age 10-13 and overweight at age 16-19.

METHODS

Adolescents and their parents (N = 3025 families), participating in a longitudinal population-based study, completed questionnaires assessing habitual bedtime and wake time on weekdays, weight and height, socioeconomic status (SES), internalizing mental health problems and disturbed eating. Two surveys were administered with a 6-year interval (T1 and T2). A one-way analysis of covariance (ANCOVA) was performed examining the association between TIB and weight category 6 years later, with SES, internalizing problems and disturbed eating at baseline entered as covariates. Hierarchical and logistic regression analyses were used to assess TIB at age 10-13 years to as a predictor of body mass index (BMI) standardized deviation scores (SDS) and overweight status at age 16-19 adjusting for the same confounders and baseline BMI.

RESULTS

A linear inverse relationship between TIB at age 10-13 and BMI category at age 16-19 was demonstrated by the ANCOVA, p < 0.001. Shorter TIB was related to higher weight, but the effect size was small (partial eta squared = 0.01). When adjusting for the included baseline confounders in the hierarchical regression model TIB significantly predicted later BMI SDS (β = -0.039, p = 0.02). The adjusted logistic regression model showed that for each hour reduction of TIB at T1 the odds of being overweight/obese at T2 increased with a factor of 1.6.

CONCLUSION

Shorter TIB was found to be a significant, yet modest, independent predictor of later weight gain in adolescence. The findings implicate that establishing healthy sleep habits should be addressed in prevention and treatment strategies for adolescent obesity.

Associations of short sleep duration with appetite-regulating hormones and adipokines: A systematic review and meta-analysis

In the current study, a systematic review and meta-analysis were conducted to summarize and assess whether short sleep duration is associated with appetite-regulating hormones and adipokine levels. Reference databases were searched for studies related to sleep and appetite-regulating hormones and adipokines. Qualitative and quantitative syntheses were conducted to evaluate the relationship between sleep duration and the level of appetite-regulating hormones and adipokines, including leptin, ghrelin, adiponectin, resistin, and orexin. Twenty-one of 3536 studies, covering a total of 2250 participants, met the inclusion criteria. Leptin, ghrelin, and adiponectin were included in the meta-analysis. Ghrelin levels were higher in the short sleep group (standard mean difference [SMD] = 0.14, 95% CI [0.03, 0.25], p = 0.01). Significant differences between the short sleep group and recommended sleep group were also noted in leptin level experimental subgroup studies (SMD = 0.19, 95% CI [0.03, 0.35], p = 0.02) and ghrelin level cross-sectional subgroup studies (SMD = 0.14, 95% CI [0.02, 0.27], p = 0.03). A rise in leptin and ghrelin levels were also observed in sleep deprivation groups (SMD = 0.24, 95% CI [0.10, 0.39], p = 0.001 and SMD = 0.18, 95% CI [0.04, 0.33], p = 0.01, respectively). In conclusion, short sleep duration is associated with an increased ghrelin level, while sleep deprivation had a significant effect on the levels of both leptin and ghrelin.

Sleep and body mass index in infancy and early childhood (6-36 mo): a longitudinal study

BACKGROUND

Relatively, few longitudinal studies have evaluated the association between sleep and body mass index (BMI) among younger children. In addition, few studies have evaluated the bidirectional longitudinal association between sleep duration and child BMI.

OBJECTIVE

The objective of the study is to determine in children aged 6 to 36 months (1) the cross-sectional association of sleep duration and sleep problems with child BMI z score, (2) whether sleep duration predicts changes in child BMI z score, and (3) and whether BMI z score can predict changes in child sleep duration.

METHODS

This study used longitudinal data from the BeeBOFT study (N = 2308). Child sleep duration and sleep problems (indicated by night awakenings and sleep-onset latency) were parent reported, and child BMI was measured using a standardized protocol by trained healthcare professionals at approximately 6, 14, and 36 months of age. Linear mixed models and linear regression models were applied to assess the cross-sectional and bidirectional longitudinal associations between sleep and BMI z scores.

RESULTS

Cross sectionally, shorter sleep duration was associated with higher BMI z scores at 14 (β = -0.034, P < 0.05) and 36 months (β = -0.045, P < 0.05). Sleep duration at 6 or 14 months did not predict BMI z score at either 14 or 36 months. Higher BMI z scores at 6 months predicted shorter sleep duration (hours) at 14 months (β = -0.129, P < 0.001). No association was found between sleep problems and child BMI z scores.

CONCLUSIONS

Cross-sectional associations between shorter sleep duration and higher BMI z score emerged in early childhood (age 14 and 36 mo). Higher BMI z scores may precede shorter sleep duration but not vice versa.