Introduction to Survival Analysis

Abstract

Suppose that one wished to study the occurrence of some event in a population of subjects. If the time until the occurrence of the event were unimportant, the event could be analyzed as a binary outcome using the logistic regression model. For example, in analyzing mortality associated with open heart surgery, it may not matter whether a patient dies during the procedure or he dies after being in a coma for two months. For other outcomes, especially those concerned with chronic conditions, the time until the event is important. In a study of emphysema, death at eight years after onset of symptoms is different from death at six months. An analysis that simply counted the number of deaths would be discarding valuable information and sacrificing statistical power.