Brenner H
Department of Epidemiology, University of Ulm, Germany.
Epidemiology. 1998 Jan;9(1):68-71.
Control of covariates is essential in nonexperimental epidemiologic studies. Important covariates, such as smoking or alcohol consumption, often are crudely categorized in epidemiologic analyses. In this paper, I illustrate by both hypothetical and empirical examples that control of crudely categorized covariates can yield strongly misleading results. In particular, I show that, under certain conditions, control for crudely classified covariates can even be worse than not controlling for such covariates at all. I conclude that covariate specification is an issue that requires much more care than it commonly receives in epidemiologic analyses.
在非实验性流行病学研究中，对协变量进行控制至关重要。重要的协变量，如吸烟或饮酒情况，在流行病学分析中常常被粗略分类。在本文中，我通过假设和实证例子说明，对粗略分类的协变量进行控制可能会产生极具误导性的结果。特别是，我表明，在某些情况下，对粗略分类的协变量进行控制甚至可能比根本不控制这些协变量更糟糕。我的结论是，协变量的设定是一个在流行病学分析中需要比通常更多关注的问题。
