Chlorinated drinking water and bladder cancer: Effect of misclassification on risk estimates

Abstract

Data are presented from the Iowa portion of the National Bladder Cancer Casecontrol Study demonstrating the effect of misclassification on depressing odds ratio estimates for years of exposure to chlorinated drinking water and bladder cancer. Four methods (METHODS 1 through 4) of quantifying chlorination exposure with sequentially decreasing degrees of misclassification are presented for the 268 bladder cancer cases and 658 population-based controls fulfilling criteria for inclusion in this study. Twenty-eight other risk factors for bladder cancer were considered along with chlorinated drinking water exposure estimated by METHOD 4. Stepwise regression models included as significant factors cigarette smoking (p