The purpose of this study is to estimate the risk of myocardial infarction (MI)/coronary death associated with use of monotherapy low dose ASA (single antiplatelet) as well as concomitant use of monotherapy low dose ASA and proton pump inhibitors (PPIs) in patients with serious coronary heart disease using two UK primary care databases.

Number of Anticipated Subjects: In case-control analysis: 10.000-15.000 participants

Inclusion Criteria:

• As above ( study population description).
• All individuals aged 50-84 years with at least one year of enrolment with the primary care physician (PCP) and a computerized prescription history of at least one year before the start of the study.

Exclusion Criteria:

• Recorded diagnosis of cancer prior to study start.
• Patients aged ≥ 70 years with a follow-up longer than one year if having fewer than two recorded consultations with a primary care physician (PCP) during their entire follow-up (proxy for incomplete and invalid data recording

Individuals aged 50-84 years who from 1 January 2000 to 31 December 2007 had a documented evidence of a hospitalization for a serious acute coronary event (MI, revascularization of coronary arteries or unstable angina) and who were alive 1 month after this event in two primary care clinical practice databases in the UK: General Practice Research Database (GPRD) and The Health Improvement Network (THIN).