The PIP-STOPP Study

The overall objective of the present study will be to describe the occurrence of Potentially Inappropriate Prescribing (PIP) in Ontario's elderly (\>65 yrs) population, assess the health and economic burden associated with it, and evaluate interventions aimed at mitigating its effects. To attain this objective, the investigators will test three specific hypotheses: Hypothesis 1: Instances of Potentially Inappropriate Prescribing are frequent and costly. To test this hypothesis, the investigators will apply a subset of the STOPP criteria and Beers criteria to Ontario health administrative data to identify instances of potentially inappropriate prescribing, and estimate potential savings, both direct and indirect, that could be achieved by reducing inappropriate prescribing. Hypothesis 2: ED visits and hospitalizations are significantly associated with Potentially Inappropriate Prescribing. To test this hypothesis, the investigators will estimate the attributable fraction of ER visits and hospitalizations associated with different frequencies of PIP using multivariate methods and survival analysis. Hypothesis 3: The likelihood of inappropriate prescribing is associated with patient and physician characteristics. To test this hypothesis, the investigators will identify each physician's annual PIP incidence density, calculated by dividing the number of PIP they issued by the total number of prescriptions they provided over the study period and then explore the association of patient and physician level covariates with patient outcomes. The investigators will test these hypotheses in the framework of a retrospective cohort study which the investigators will conduct using Ontario's large health administrative and population databases. These are housed at the Institute for Clinical Evaluative Sciences (ICES) and contain information on both hospital and outpatient use of health services, as well as demographic and socioeconomic data. Patients included in the study will