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A Simulation Study of Categorizing Continuous Exposure Variables Measured with Error in Autism Research: Small Changes with Large Effects
Journal article   Open access   Peer reviewed

A Simulation Study of Categorizing Continuous Exposure Variables Measured with Error in Autism Research: Small Changes with Large Effects

Karyn Heavner and Igor Burstyn
International journal of environmental research and public health, v 12(8), pp 10198-10234
24 Aug 2015
PMID: 26305250
url
https://doi.org/10.3390/ijerph120810198View
Published, Version of Record (VoR)CC BY V4.0 Open

Abstract

Autistic Disorder - chemically induced Autistic Disorder - epidemiology Computer Simulation Environmental Exposure Environmental Pollutants - toxicity Humans Logistic Models Longitudinal Studies Models, Theoretical Odds Ratio Research Design Sensitivity and Specificity
Variation in the odds ratio (OR) resulting from selection of cutoffs for categorizing continuous variables is rarely discussed. We present results for the effect of varying cutoffs used to categorize a mismeasured exposure in a simulated population in the context of autism spectrum disorders research. Simulated cohorts were created with three distinct exposure-outcome curves and three measurement error variances for the exposure. ORs were calculated using logistic regression for 61 cutoffs (mean ± 3 standard deviations) used to dichotomize the observed exposure. ORs were calculated for five categories with a wide range for the cutoffs. For each scenario and cutoff, the OR, sensitivity, and specificity were calculated. The three exposure-outcome relationships had distinctly shaped OR (versus cutoff) curves, but increasing measurement error obscured the shape. At extreme cutoffs, there was non-monotonic oscillation in the ORs that cannot be attributed to "small numbers." Exposure misclassification following categorization of the mismeasured exposure was differential, as predicted by theory. Sensitivity was higher among cases and specificity among controls. Cutoffs chosen for categorizing continuous variables can have profound effects on study results. When measurement error is not too great, the shape of the OR curve may provide insight into the true shape of the exposure-disease relationship.

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Web of Science research areas
Environmental Sciences
Public, Environmental & Occupational Health
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