Sleep- an Elixer to Combat Obesity?

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Evidence shows the importance of getting a good night’s sleep- 7 hours seems to be the magic number; more or less is associated with negative implications for blood pressure, weight, and blood sugar. Less sleep or disrupted sleep, like graveyard-shift workers, likely disrupt the natural circadian rhythms which can shift the hormonal milieu toward increased hunger cues which can lead to higher calorie consumption and perhaps the consumption of more processed foods. We also know that sleep quality and duration change as we age, as babies, we need a lot of sleep to support brain development; this continues into early adulthood.

A new study by Jiao Wang and colleagues from the University of Hong Kong in the Journal Obesity examines the role of sleep duration and adiposity (body fat) in children and adults. The study sample included children from the “Children of 1997 birth cohort” a population representative of Chinese birth cohort that covered 88% of all births in China in 1997. Children were followed over multiple time points as they aged, and a survey derived sleep duration measure was obtained from parents who reported if their child slept more or less than 9 hours a night. Children also had six annual weight and height assessments annually between the ages of 11 to 16. The authors also had access to genetically predictive sleep duration data as part of a broader genome study. The sample drew from had 8,237 children, and the final sample of 3,614 children showed 24.6 had overweight, and 4.3% had obesity.

Findings suggest that short sleep duration was associated with higher BMI in the study sample with a stronger inverse association in girls when compared to boys. On examining the genetic data (Mendelian randomization), sleep duration was inversely associated with BMI in children, but this finding was not seen in adults.

Overall we have some signals that in children sleep duration and adiposity are linked, but these findings don’t hold for adults.  A few limitations should be pointed out. Firstly, the sample used self-reported sleep from parents whose recall would not be as accurate as sleep device-derived data; it is a method that has been used in many other studies but is subject to bias in the recall of events. Secondly, the study did not address nutritional intake in the study years, so it was difficult to determine if that was a factor in this study. We also know the hormonal changes that occur in puberty, which in turn influence body composition may also be a factor to consider.

I would like to see this study conducted in a larger sample with more accurate measures of sleep duration. We still know sleep is essential for health but the science on exactly why needs to evolve.

Thanks for reading – Trina
(Opinions are my own)

Sleep duration and adiposity in children and adults

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