Mittleman M A, Maclure M, Robins J M
Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA.
Am J Epidemiol. 1995 Jul 1;142(1):91-8. doi: 10.1093/oxfordjournals.aje.a117550.
The case-crossover study design is a method to assess the effect of transient exposures on the risk of onset of acute events. Control information for each case is based on his/her past exposure experience, and a self-matched analysis is conducted. Empiric evaluation of five approaches to the analysis of case-crossover data from a study of heavy physical exertion and acute myocardial infarction onset is shown. The data presented are from the Onset Study, a case-crossover study of the determinants of myocardial infarction onset conducted in 45 centers from August 1989 to October 1992. In model 1, exactly one control period (matched on clock-time) was sampled per case. In models 2-4, up to 25 control periods were sampled, and the effect of clock-time on the baseline hazard of infarction was modeled. In model 5, a census of the person-time experienced by each subject over the year preceding the infarction was sampled. The 95% confidence interval for model 1 was 2.7 times wider, and the relative efficiency, defined as v infinity/vM, where vM represents the asymptotic variance estimate of the estimated log relative risk with M control periods sampled per case, was only about 14% of model 5. In models 2-4, the efficiency increased with the number of control periods, regardless of the modeling assumptions. Even with many control periods sampled, models 2-4 achieved only half the efficiency of model 5. The control sampling strategy in any given case-crossover study should be selected with the trade-offs between precision and potential biases of the estimates in mind.
病例交叉研究设计是一种评估短暂暴露对急性事件发病风险影响的方法。每个病例的对照信息基于其过去的暴露经历，并进行自我匹配分析。文中展示了对重体力活动与急性心肌梗死发病研究中的病例交叉数据进行分析的五种方法的实证评估。所呈现的数据来自发病研究，这是一项于1989年8月至1992年10月在45个中心进行的关于心肌梗死发病决定因素的病例交叉研究。在模型1中，每个病例精确抽取一个对照期（按时间匹配）。在模型2 - 4中，抽取多达25个对照期，并对时间对梗死基线风险的影响进行建模。在模型5中，对每个受试者在梗死前一年经历的人时进行普查抽样。模型1的95%置信区间宽2.7倍，相对效率（定义为v无穷/vM，其中vM表示每个病例抽取M个对照期时估计对数相对风险的渐近方差估计值）仅为模型5的约14%。在模型2 - 4中，无论建模假设如何，效率都随着对照期数量的增加而提高。即使抽取了许多对照期，模型2 - 4的效率也仅达到模型5的一半。在任何给定的病例交叉研究中，选择对照抽样策略时应考虑估计值的精度和潜在偏差之间的权衡。
