Imputation of missing dates of death or institutionalization for time-to-event analyses in the Canadian Study of Health and Aging

Data from the Canadian Study of Health and Aging (CSHA) allow investigators to study patterns and predictors of mortality and institutional placement in a well characterized, population-based cohort of elderly Canadians. However, it is impossible to study the timing of these events if the date of occurrence is missing. This technical article describes a procedure for imputing missing dates of death or institutionalization. The first step consists in identifying and correcting dates that are inconsistent with other available dates on which we know the event has or has not occurred. A missing date for an event is then replaced by the middle of a range of plausible dates for its occurrence. This constitutes a valuable addition to the CSHA data since it precludes the loss of information that results from discarding subjects with missing occurrence dates in time-to-event analyses.