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arXiv 0712.0660stat.AP
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因果推断中现实的个体化处理规则的重要性的实际例证

A practical illustration of the importance of realistic individualized treatment rules in causal inference

Oliver Bembom, Mark J. van der Laan

摘要:

使用传统的因果推断方法难以估计剧烈体育活动对老年人死亡率的影响,传统方法通过比较与假设情景对应的死亡率风险来定义这种影响,在假设情景中,目标人群中的所有受试者都从事给定水平的剧烈体育活动。只有当目标人群中的所有受试者都有选择每种候选治疗方案的正概率时,才能从观察到的数据中识别基于此类静态治疗干预定义的因果效应,在这种情况下,这一假设是非常不现实的,因为患有严重健康问题的受试者将无法进行更高水平的剧烈体力活动。这个问题可以通过关注因果效应来解决,这些因果效应是基于现实的个性化治疗规则和意向治疗规则定义的,这些规则明确考虑了每个受试者可用的治疗选项集。我们提出了一个数据分析,说明静态因果效应的估计,事实上往往高估了高水平的剧烈体力活动的有益影响,而相应的估计,基于现实的个性化治疗规则和意向治疗规则可以产生无偏估计。我们强调,在估计静态因果效应时遇到的问题并不局限于IPTW估计,但也观察到与$G$计算估计,DR-IPTW估计,和有针对性的MLE。我们基于现实的个体化治疗规则和意向治疗规则的分析表明,高水平的剧烈体力活动可能会使死亡风险降低15- 30%,尽管在大多数情况下,这种效果的证据并没有达到0.05的显著性水平。

英文摘要:

The effect of vigorous physical activity on mortality in the elderly is difficult to estimate using conventional approaches to causal inference that define this effect by comparing the mortality risks corresponding to hypothetical scenarios in which all subjects in the target population engage in a given level of vigorous physical activity. A causal effect defined on the basis of such a static treatment intervention can only be identified from observed data if all subjects in the target population have a positive probability of selecting each of the candidate treatment options, an assumption that is highly unrealistic in this case since subjects with serious health problems will not be able to engage in higher levels of vigorous physical activity. This problem can be addressed by focusing instead on causal effects that are defined on the basis of realistic individualized treatment rules and intention-to-treat rules that explicitly take into account the set of treatment options that are available to each subject. We present a data analysis to illustrate that estimators of static causal effects in fact tend to overestimate the beneficial impact of high levels of vigorous physical activity while corresponding estimators based on realistic individualized treatment rules and intention-to-treat rules can yield unbiased estimates. We emphasize that the problems encountered in estimating static causal effects are not restricted to the IPTW estimator, but are also observed with the $G$-computation estimator, the DR-IPTW estimator, and the targeted MLE. Our analyses based on realistic individualized treatment rules and intention-to-treat rules suggest that high levels of vigorous physical activity may confer reductions in mortality risk on the order of 15-30%, although in most cases the evidence for such an effect does not quite reach the 0.05 level of significance.

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