A comparison of standing steadiness measurements from two devices: covariates and normal values

Quantifying standing steadiness may be a useful method of detecting neurotoxicity in epidemiological studies. Unfortunately, use of quantitative standing steadiness outcomes in epidemiologic studies has been limited by lack of standardization of methods, insufficient availability of normative data, and inadequately characterized effects of covariates. Additionally, the current gold standard method, the force platform (FP), has been expensive and unwieldy for use in field studies. A relatively inexpensive and portable head position monitor (HPM) has been introduced as an alternate method for measuring standing steadiness. In this study 211 subjects were tested with one or both devices using a common testing protocol. The correlations between measurements obtained with the FP and the HPM were high and similar to those obtained during repeated measurements with each device separately. The effects of potential covariates on outcome measures were investigated. There was significant age x sex interaction in the FP standing steadiness measurements in this population with decreased steadiness among older men but not older women. Information for estimating normal values for the outcome measures is provided. This study suggests that measures of standing steadiness obtained with the HPM are similar, but not identical, to measures obtained with a conventional FP and that the HPM may be useful in field studies of occupational exposure to neurotoxicants.