For each patient we identified all prescriptions for statins before the index date (atorvastatin, cerivastatin, fluvastatin, pravastatin, simvastatin). Episodes of statin treatment were defined as a series of subsequent prescription refills for these drugs. We assumed that a new episode of treatment started if an interval of 14 days or more occurred between the theoretical end date of a prescription and the date of the next prescription for the same patient. The theoretical end date was defined as the prescription date plus the duration of use (number of tablets prescribed divided by the prescribed daily dose). Patients were classified as current statin users when the index date was between the start and the end date of a treatment episode. Patients were classified as past users when they were not a current user but had a history of use in the year before the index date.