慢性病研究中的混杂效应修饰与生态偏倚的关系

The Relationship between Confounding, Effect Modification and Ecological Bias

生态偏倚有时归因于组变量(生态分析单位)的混杂,或与组变量有关的危险因素.不管组变量或效应修饰因子是否独立的危险因素,效应修饰可导致很大的生态偏倚.此外,引起生态偏倚的其他危险因素,其本身不一定在个体水平上与研究变量有关.这样,因协同变量导致生态偏倚的条件比因其导致个体水平的混杂的条件要广泛得多.与生态偏倚有关的变量的标化或生态控制,一般不能充分地消除这种偏倚.

Ecological bias is sometimes attributed to confouding by the group variable (ie, unit (or ecological analysis), or to risk factors associated with the group variable. Effect modification can lead to profound ecological bias. whet her or not the group variable or the effect modifier are independent risk factors. An extraneous risk factor need not be associated with the study variable at the individual level in order to produce ecological bias. Thus the conditions for the production of ecological bias by a covarite are much broader than the conditions for the production of individual level confounding by a covariate. Standardization or ecological control of variables responsible for ecological bias are generally insufficient to remove such bias.