title: A statistical model for interpreting computerized dynamic posturography data.
abstract: Computerized dynamic posturography (CDP) is widely used for assessment of altered balance control. CDP trials are quantified using the equilibrium score (ES), which ranges from zero to 100, as a decreasing function of peak sway angle. The problem of how best to model and analyze ESs from a controlled study is considered. The ES often exhibits a skewed distribution in repeated trials, which can lead to incorrect inference when applying standard regression or analysis of variance models. Furthermore, CDP trials are terminated when a patient loses balance. In these situations, the ES is not observable, but is assigned the lowest possible score--zero. As a result, the response variable has a mixed discrete-continuous distribution, further compromising inference obtained by standard statistical methods. Here, we develop alternative methodology for analyzing ESs under a stochastic model extending the ES to a continuous latent random variable that always exists, but is unobserved in the event of a fall. Loss of balance occurs conditionally, with probability depending on the realized latent ES. After fitting the model by a form of quasi-maximum-likelihood, one may perform statistical inference to assess the effects of explanatory variables. An example is provided, using data from the NIH/NIA Baltimore Longitudinal Study on Aging.
authors.affiliation: National Aeronautics and Space Administration, Johnson Space Center, Houston, TX 77058, USA. alan.h.feiveson1@jsc.nasa.gov
authors.forename: Alan H
authors.initials: AH
authors.lastname: Feiveson
authors.forename: E Jeffrey
authors.initials: EJ
authors.lastname: Metter
authors.forename: William H
authors.initials: WH
authors.lastname: Paloski
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D006801:Humans; D016013:Likelihood Functions; D008875:Middle Aged; D015233:Models, Statistical; D004856:Postural Balance / Q000502:physiology*