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Abstract:
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The paper considers clinical trials where multiple occurrences of the same event are recorded over time. I will first consider the case without terminal events, focusing on, the Poisson and the frailty-Poisson model, with a proportional hazards assumption. The frailty-Poisson model shows the same treatment effect unconditionally as conditionally on the frailty. From this we will learn that studying the first event only is insufficient because the unconditional effect is smaller than the conditional. We will also learn that a rate model may target the same treatment effect as the frailty model. Terminal events make the case more complicated because events cannot occur after death and therefore we need to be concerned whether any suggested analysis technique could make a treatment with high mortality appear as successful in reducing the number of events. The suggestion is to consider the integrated hazard of events even though this probably falls outside the estimand definition.
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