Sleep Duration and Adiposity in Children and Adults: Observational and Mendelian Randomization Studies

Abstract

Objective: This study used two complementary designs, an observational and a Mendelian randomization (MR) study, to assess whether sleep duration causes adiposity in children and adults. Methods: In Hong Kong's "Children of 1997" birth cohort, the adjusted cross-sectional associations of sleep duration with BMI z score and obesity and overweight were assessed at ~11 years of age. Generalized estimating equations were also used to examine longitudinal associations of sleep duration at ~11 years with annual BMI z score and obesity and overweight at about 11 to 16 years of age. Using MR, this study assessed the association of genetically predicted sleep duration based on 54 singlenucleotide polymorphisms, applied to genetic studies of adiposity in children (n = 35,668), men (n = 152,893), and women (n = 171,977). Results: Longer sleep was cross-sectionally associated with lower BMI z score at ~11 years of age (−0.13 per category, 95% CI: −0.22 to −0.04) and at about 11 to 16 years of age longitudinally in girls (−0.39, 95% CI: −0.66 to −0.13). Using MR, sleep duration was inversely associated with BMI in children (−0.29 SD per hour, 95% CI: −0.54 to −0.04), but was not clearly associated with BMI in adults, particularly for women. Conclusions: A small beneficial effect of sleep on BMI in children cannot be ruled out.

Age of puberty and Sleep duration: Observational and Mendelian randomization study

“…However, the same direction of effect estimates in women and men in the MR study suggests a role for pubertal timing in sleep duration in general rather than menarche specifically. Together with evidence of a similar causal effect of age of voice breaking on obesity and cardio metabolic traits 24 , our results could indicate sleep duration is a marker, not a driver, of obesity 40 and possibly other chronic diseases.…”

Sleep duration: A review of genome-wide association studies (GWAS) in adults from 2007 to 2020

“…glycaemic traits [50], cardiovascular disease and lipid profiles [51], haemoglobin and haematocrit [52], adiposity [53] and cognitive function and dementia [54]. The MR study of sleep duration and cognitive function/dementia was also the first to employ non-linear MR methods to try to understand the causal nature of the U-shaped association between sleep duration and these phenotypes.…”

“…Thus, we must be sure that these SNPs are also relevant to children and adolescents, as for some complex traits heritability may differ by age [58]. This is also important because some of the MR studies published to date have been in paediatric/adolescent cohorts [47,52,53] and have used the sleep duration SNPs discovered and replicated in adults. Fourthly, the divergence between SNP heritability estimates for objective (19%) vs. self-reported sleep duration (9.8%) raise questions and this is important to consider, given that the majority of cohort studies still only collect selfreported data, for obvious reasons.…”

Association of Sleep Duration with Weight Gain and General and Central Obesity Risk in Chinese Adults: A Prospective Study

“…Short sleepers are more likely to have lower physical activity levels and resting metabolic rate . However, the causal relationship between short sleep duration and weight gain remains uncertain, as a recent Mendelian randomization study failed to link sleep duration with obesity in adults, although some effects were observed in children . Further research is needed to confirm the causal relationship between short sleep duration and obesity risk.…”