Alderman B W, Barón A E, Savitz D A
Department of Epidemiology, University of Washington, Seattle 98195.
Am J Epidemiol. 1993 Jun 1;137(11):1259-72. doi: 10.1093/oxfordjournals.aje.a116628.
When lacking information on confounding variables, epidemiologists have used surrogates which are antecedents of both the exposures and confounders of interest. The usefulness of this strategy is explored in a series of scenarios for a prospective epidemiologic study wherein risk ratios relating antecedent to confounder, antecedent to exposure, and confounder to exposure were varied. Antecedent-adjusted, confounder-adjusted, and crude risk ratios were calculated and compared. The antecedent-adjusted risk ratio was useful, that is, was closer to the confounder-adjusted risk ratio than was the crude risk ratio, in 1,067 (49%) of 2,187 scenarios. The antecedent-adjusted risk ratio, the crude risk ratio, and the risk ratio relating confounder to exposure together predicted the usefulness of the antecedent (or any variable) as a confounder proxy. The antecedent was useful in 97% of scenarios wherein: 1) the antecedent-adjusted risk ratio was less than the crude risk ratio, and the risk ratio relating confounder to exposure was greater than 1.0, or 2) the antecedent-adjusted risk ratio was greater than the crude risk ratio, and the risk ratio relating confounder to exposure was less than 1.0. In the remaining scenarios, it was useful only 5% of the time.
在缺乏混杂变量信息时，流行病学家会使用替代变量，这些替代变量是感兴趣的暴露因素和混杂因素的先行因素。在一系列前瞻性流行病学研究的场景中探讨了这种策略的有效性，其中先行因素与混杂因素、先行因素与暴露因素以及混杂因素与暴露因素之间的风险比各不相同。计算并比较了先行因素调整后的、混杂因素调整后的和粗风险比。在2187个场景中的1067个（49%）场景中，先行因素调整后的风险比是有用的，也就是说，它比粗风险比更接近混杂因素调整后的风险比。先行因素调整后的风险比、粗风险比以及混杂因素与暴露因素之间的风险比共同预测了先行因素（或任何变量）作为混杂因素替代指标的有效性。在97%的场景中先行因素是有用的，这些场景为：1）先行因素调整后的风险比小于粗风险比，且混杂因素与暴露因素之间的风险比大于1.0，或者2）先行因素调整后的风险比大于粗风险比，且混杂因素与暴露因素之间的风险比小于1.0。在其余场景中，它只有5%的时间是有用的。
