Validation of the Entrainment Signal Regularity Index and associations with children's changes in BMI

Authors: MORENO, JENNETTE - Children'S Nutrition Research Center (CNRC); HANNAY, KEVIN - University Of Michigan; GOETZ, AMY - Baylor College Of Medicine; WALCH, OLIVIA - University Of Michigan; CHENG, PHILIP - Henry Ford Hospital

Submitted to: Obesity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/30/2022
Publication Date: 1/11/2023
Citation: Moreno, J.P., Hannay, K.M., Goetz, A.R., Walch, O., Cheng, P. 2023. Validation of the Entrainment Signal Regularity Index and associations with children's changes in BMI. Obesity. https://doi.org/10.1002/oby.23641.
DOI: https://doi.org/10.1002/oby.23641

Interpretive Summary: The Hannay Model of circadian entrainment has been shown to predict children's circadian phase using data from wearable devices within +/- 31 minutes of the gold standard assessment of circadian phase (dim light melatonin onset). The Entrainment Signal Regularity Index is a novel metric of circadian health. Entering wearable activity data into the Hannay Model, the ESRI quantifies the change in model amplitude over time. Stronger, more regular, and more appropriately timed activity patterns produce greater increases in amplitude, resulting in a higher ESRI. The purpose of this study was to examine the validity of a novel metric of circadian health, the Entrainment Signal Regularity Index (ESRI), and its relationship to changes in BMI during the school year and summer. In a longitudinal observational dataset, we examined the relationship between the ESRI and children's (n=119, 5–8-year-olds) sleep and physical activity (PA) levels during the school year and summer, differences in the ESRI during the school year and summer, and the association of the ESRI during the school year and summer with changes in BMI across those time periods. The ESRI was higher during the school year compared to summer. After controlling for sleep midpoint, sleep regularity, and activity levels, having a lower ESRI during summer predicted greater changes in BMI during summer. Overall, children demonstrated higher entrainment regularity during the school year compared to the summer. During summer, having a higher entrainment signal was associated with smaller changes in summertime BMI. This effect was independent of the effects of children's sleep midpoint, sleep regularity, and PA on children's BMI. These findings suggest that the timing of physical activity (PA) relative to one's circadian phase might have a stronger impact on change in BMI than the total amount of PA that children engage in. Further research is needed to understand how the ESRI is related to changes in children's BMI.

Technical Abstract: This study examined the validity of a novel metric of circadian health, the Entrainment Signal Regularity Index (ESRI), and its relationship to changes in BMI during the school year and summer.In a longitudinal observational data set, this study examined the relation-ship between ESRI score and children's (n=119, 5- to 8-year-olds) sleep and physical activity levels during the school year and summer, differences in ESRI score during the school year and summer, and the association of ESRI score during the school year and summer with changes in BMI across those time periods. The ESRI score was higher during the school year (0.70+/-0.10) compared with summer (0.63+/-0.11); t(111)=5.484, p<0.001. Whereas the ESRI score at the beginning of the school year did not significantly predict BMI change during the school year (Beta=0.05+/-0.09 SE, p=0.57), having a higher ESRI score during summer predicted smaller increases in BMI during summer (Beta=-0.22+/-0.10 SE, p=0.03). Overall, children demonstrated higher entrainment regularity during the school year compared with the summer. During summer, having a higher entrainment signal was associated with smaller changes in summertime BMI. This effect was inde-pendent of the effects of children's sleep midpoint, sleep regularity, and physical activity on children’s BMI.