Multi-level zero-inflated poisson regression modelling of correlated count data with excess zeros

Stat Methods Med Res. 2006 Feb;15(1):47-61. doi: 10.1191/0962280206sm429oa.

Abstract

Count data with excess zeros relative to a Poisson distribution are common in many biomedical applications. A popular approach to the analysis of such data is to use a zero-inflated Poisson (ZIP) regression model. Often, because of the hierarchical study design or the data collection procedure, zero-inflation and lack of independence may occur simultaneously, which render the standard ZIP model inadequate. To account for the preponderance of zero counts and the inherent correlation of observations, a class of multi-level ZIP regression model with random effects is presented. Model fitting is facilitated using an expectation-maximization algorithm, whereas variance components are estimated via residual maximum likelihood estimating equations. A score test for zero-inflation is also presented. The multi-level ZIP model is then generalized to cope with a more complex correlation structure. Application to the analysis of correlated count data from a longitudinal infant feeding study illustrates the usefulness of the approach.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Breast Feeding / statistics & numerical data
  • Female
  • Humans
  • Infant
  • Infant, Newborn
  • Longitudinal Studies
  • Male
  • Models, Statistical
  • Poisson Distribution*
  • Regression Analysis*
  • Western Australia