Higher Potency Statins and the Risk of New Diabetes: Multicentre, Observational Study of Administrative Databases

The study objective is to determine whether the use of high potency statins, compared with the use of low potency statins, is associated with an increased risk of incident diabetes following hospitalisation for a cardiovascular event or procedure. The investigators will use a common-protocol approach to conduct retrospective cohort studies using health care data from eight jurisdictions (the Canadian provinces of Alberta, Manitoba, Nova Scotia, Ontario, Quebec, and Saskatchewan, as well as the United States (US) MarketScan and the United Kingdom (UK) Clinical Practice Research Datalink [CPRD]). The Canadian provincial databases contain information on physician billing, diagnoses and procedures from hospital discharge abstracts, and dispensations for prescription drugs at a population level. The CPRD is a clinical database that is representative of the UK population and contains the records for patients seen at over 680 general practitioner practices in the UK; these data will be linked to the Hospital Episode Statistics (HES) database, which contains in-hospital diagnosis and procedure data. US MarketScan includes individuals and their dependents covered by large U.S. employer health insurance plans, and government and public organizations.

Study population

In each jurisdiction, the investigators will assemble a study cohort that includes all patients with a new prescription for a statin (after hospital discharge), including simvastatin, lovastatin, pravastatin, fluvastatin, atorvastatin, and rosuvastatin, from the earliest availability of data at each site to the last date of available data. The date of study cohort entry is defined by the prescription date of the newly-prescribed statin. Patients will be followed from the date of study cohort entry until an event (defined below) or censoring due to death, departure from the database, 24 months after the initiation of statin treatment, a dispensing for cerivastatin, or the end of the study period (31 March 2011 or the last date of data availability at that site), whichever occurs first. Data from Alberta, Ontario, and Nova Scotia will be restricted to patients aged 65 years and older as prescription data are not available for younger patients.

Case-control selection

The cohort defined above will be analyzed using a nested case-control analysis, where cases are defined as a hospitalization for incident diabetes or the prescription for an insulin or an oral antidiabetic medication. Risk set sampling will be used to randomly select up to 10 controls for each case, matched on sex, age (± two years; however, if no controls are available, within five years), and cohort entry (± 90 days).