What percentage of Children in the US are Eating a Healthy Diet? A Statistical Approach
by Professor Raymond J Carroll
Abstract: In the United States the preferred method of obtaining dietary intake data is the 24-hour dietary recall, yet the measure of most interest is usual or long-term average daily intake, which is impossible to measure. Thus, usual dietary intake is assessed with considerable measurement error. Also, diet represents numerous foods, nutrients and other components, each of which have distinctive
attributes. Sometimes, it is useful to examine intake of these components separately, but increasingly nutritionists are interested in exploring them collectively
to capture overall dietary patterns. Consumption of these components varies
widely: some are consumed daily by almost everyone on every day, while others
are episodically consumed so that 24-hour recall data are zero inflated. In addition, they are often correlated with each other. Finally, it is often preferable to analyze the amount of a dietary component relative to the amount of energy
(calories) in a diet because dietary recommendations often vary with energy level. The quest to understand overall dietary patterns of usual intake has to this point reached a standstill. There are no statistical methods or models available to model such complex multivariate data with its measurement error and zero inflation. This paper proposes the first such model, and it proposes the first workable solution to fit such a model. After describing the model, we
use survey-weighted MCMC computations to fit the model, with uncertainty
estimation coming from balanced repeated replication. The methodology is illustrated through an application to estimating the population distribution of
the Healthy Eating Index-2005 (HEI-2005), a multi-component dietary quality index involving ratios of interrelated dietary components to energy, among children aged 2-8 in the United States. We pose a number of interesting questions about the HEI-2005 and provide answers that were not previously within the
realm of possibility, and we indicate ways that our approach can be used to
answer other questions of importance to nutritional science and public health.
This work is part of the Ph.D. dissertation of Saijuan Zhang.
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