Page 181 - Contributed Paper Session (CPS) - Volume 4

CPS2169 Carmen D. Tekwe et al.
Percentile-based approaches for assessing
impacts of school day energy expenditure on 18-
month change in bmi among elementary school-
aged children
3
1
2
1
Carmen D. Tekwe , Gilson Honvoh , Roger S. Zoh, Lan Xue , Anand Gupta ,
Mark Benden
4
1 Department of Epidemiology and Biostatistics Indiana University, Bloomington, IN
2 Department of Biostatistics, University of North Carolina, Chapel Hill, NC
3 OhioHealth, Columbus, OH
4 Department of Environmental and Occupational Health, Texas A&M University, College
Station, Texas

Abstract
Childhood obesity is defined based on age- and sex- adjusted body mass
indexes (BMI) within upper percentile ranges. Most studies assessing impacts
of interventions on BMI rely on traditional linear regression models designed
to assess intervention effects on children within "normal" BMI percentile
ranges, limiting assessments of how interventions affect children at higher
risks for overweight and obesity. Thus, statistical approaches that permit
evaluations of intervention effects across the full distribution of BMI are more
desirable for determining their impacts on subjects at higher risks for
developing overweight or obesity. In this manuscript, we determine the
association between energy expenditure obtained at a prior time on
subsequent risk or progression to obesity. We describe the use of conditional
functional quantile regression models to study the relationship between
school day energy expenditure, a function-valued covariate, and BMI. Through
empirical comparisons, we present the results from mean regression and
quantile regression- based models. The benefits of using quantile regression-
based methods in assessing intervention effects in obesity research are also
discussed.

Keywords
B-splines, Cluster randomized trial, Functional data analysis, Physical activity,
Quantile regression

1. Introduction
About 90% of children diagnosed with type 2 diabetes are either
overweight or obesity patients (Liu, et al. 2010). While it is well known that
obesity results from a chronic imbalance between energy expenditure and
energy intake, as well as from environmental exposures and genetic
predisposition, the exact role of energy expenditure in obesity development is
unclear (Bandini, et al. 2004). To combat this growing epidemic among
children, behavioural researchers are increasingly interested in employing

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