Researchers at various institutions in Australia came together to conduct research on sleep habits and body mass index (BMI) in children. It is no surprise that sleep is at the center of another scientific study. Adequate sleep is necessary for survival and it happens to be an explanatory variable for many topics related to the health of the body. Body mass index is often used when discussing the health of a child. If it is such a critical aspect of assessing the health of a child, then it is valuable to identify what factors contribute to it. Researchers in Australia planned to do just that. They intended to explore the sleep patterns of children and determine if sleep is associated with body mass index.

Researchers used data provided by the LSIC (longitudinal study conducted by the Department of Social Services, Australia). There were approximately 1000 child participants. Each child’s sleeping patterns were identified via a face-to-face survey. The parents or guardians of the child reported the child’s


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entire sleep schedule. This included wake up time on school nights, school night sleep duration, and weekend bedtime. In addition, each child was measured for height and weight. The results were used to calculate their BMI. The sleep schedule survey and the BMI measurements were taken periodically over the course of a few years.

The results are in… are you ready? Researchers created a 5-class model in which they placed each child based on their sleeping habits. The classes were as follows: 1) early/long sleepers 2) normative sleepers-typical sleep patterns 3) late sleepers 4) consistent late sleepers and 5) early risers. The percentages of children in each class were 4.53%, 25.5%, 49.9%, 11.1%, and 9%, respectively. The largest group consisted of children that went to bed later than the rest of the population with typical sleep patterns. Now how does this relate to BMI? The results suggested that children who were consistently late sleepers had the largest increase in BMI overtime. In comparison, the children who were early risers had the smallest increase in BMI overtime. Overall, the results suggested that a late bedtime is associated with childhood obesity (indicative of a high BMI).

I would be remiss if I did not acknowledge the impact other variables can have on the results. Researchers found that food choices and socioeconomic disadvantages can impact sleep patterns and in turn result in BMI gain overtime. Before you start sending your kids to bed super early each night, it is important to realize that every child is different. Sleep may impact BMI, but there are other factors that contribute to BMI as well.

Fatima, Y., Mamun, A.A., Bucks, R.S., & Skinner, T.C. 2020. Late bedtime and body mass index gain in indigenous Australian children in the longitudinal study of indigenous children. Acta Paediatrica 1: 1-7.