A mixed-effects model approach for estimating the distribution of usual intake of nutrients: The NCI method
Article first published online: 22 SEP 2010
Copyright © 2010 John Wiley & Sons, Ltd.
Statistics in Medicine
Volume 29, Issue 27, pages 2857–2868, 30 November 2010
How to Cite
Tooze, J. A., Kipnis, V., Buckman, D. W., Carroll, R. J., Freedman, L. S., Guenther, P. M., Krebs-Smith, S. M., Subar, A. F. and Dodd, K. W. (2010), A mixed-effects model approach for estimating the distribution of usual intake of nutrients: The NCI method. Statist. Med., 29: 2857–2868. doi: 10.1002/sim.4063
- Issue published online: 11 NOV 2010
- Article first published online: 22 SEP 2010
- Manuscript Accepted: 26 JUL 2010
- Manuscript Received: 2 NOV 2009
- statistical distributions;
- diet surveys;
- nutrition assessment;
- mixed-effects model;
It is of interest to estimate the distribution of usual nutrient intake for a population from repeat 24-h dietary recall assessments. A mixed effects model and quantile estimation procedure, developed at the National Cancer Institute (NCI), may be used for this purpose. The model incorporates a Box–Cox parameter and covariates to estimate usual daily intake of nutrients; model parameters are estimated via quasi-Newton optimization of a likelihood approximated by the adaptive Gaussian quadrature. The parameter estimates are used in a Monte Carlo approach to generate empirical quantiles; standard errors are estimated by bootstrap. The NCI method is illustrated and compared with current estimation methods, including the individual mean and the semi-parametric method developed at the Iowa State University (ISU), using data from a random sample and computer simulations. Both the NCI and ISU methods for nutrients are superior to the distribution of individual means. For simple (no covariate) models, quantile estimates are similar between the NCI and ISU methods. The bootstrap approach used by the NCI method to estimate standard errors of quantiles appears preferable to Taylor linearization. One major advantage of the NCI method is its ability to provide estimates for subpopulations through the incorporation of covariates into the model. The NCI method may be used for estimating the distribution of usual nutrient intake for populations and subpopulations as part of a unified framework of estimation of usual intake of dietary constituents. Copyright © 2010 John Wiley & Sons, Ltd.