Hartemink Nienke, Boshuizen Hendriek C, Nagelkerke Nico J D, Jacobs Monique A M, van Houwelingen Hans C
National Institute of Public Health and the Environment, Bilthoven, the Netherlands.
Am J Epidemiol. 2006 Jun 1;163(11):1042-52. doi: 10.1093/aje/kwj141. Epub 2006 Apr 12.
Studies on a dose-response relation often report separate relative risks for several risk classes compared with a referent class. When performing a meta-analysis of such studies, one has to convert these relative risks into an overall relative risk for a continuous effect. Apart from taking the dependence between separate relative risks into account, this implies assigning an exposure level to each risk factor class and allowing for the nonlinearity of the dose-response relation. The authors describe a relatively simple method solving these problems. As an illustration, they applied this method in a meta-analysis of the association between body mass index and diabetes type 2, restricted to results of follow-up studies (n=31). Results were compared with a more ad hoc method of assigning exposure levels and with a method in which the nonlinearity of the dose-response method was not taken into account. Differences with the ad hoc method were larger in studies with fewer categories. Not incorporating the nonlinearity of the dose response leads to an overestimation of the pooled relative risk, but this bias is relatively small.
关于剂量反应关系的研究通常会报告与参照类别相比，几个风险类别的单独相对风险。在对此类研究进行荟萃分析时，必须将这些相对风险转换为连续效应的总体相对风险。除了考虑单独相对风险之间的依赖性之外，这还意味着为每个风险因素类别指定一个暴露水平，并考虑剂量反应关系的非线性。作者描述了一种解决这些问题的相对简单的方法。作为一个例子，他们将这种方法应用于体重指数与2型糖尿病关联的荟萃分析中，该分析仅限于随访研究的结果（n = 31）。将结果与一种更临时的暴露水平分配方法以及一种未考虑剂量反应方法非线性的方法进行了比较。在类别较少的研究中，与临时方法的差异更大。不纳入剂量反应的非线性会导致对合并相对风险的高估，但这种偏差相对较小。
