Cardiovascular risk factors and diseases precede oral hypoglycaemic therapy in patients with type 2 diabetes mellitus

Although patients with type 2 diabetes mellitus and cardiovascular disease share common risk factors, the link between these diseases remains largely unexplained. In this case-control study, the earlier use of cardiovascular drugs (before the diagnosis of diabetes) was investigated among cases with type 2 diabetes mellitus and controls without diabetes. Using the PHARMO database, we identified 4,864 patients who were prescribed oral hypoglycaemic agent (OHA) therapy between 1985-1998 in the Netherlands. For each case, two controls matched on age, sex and pharmacy were randomly selected. Controls had not received insulins or OHA therapy. There were 2,656 (55.0%) cases compared with 2,727 (28.1%) controls who used cardiovascular drugs at the start of OHA therapy. Cases had a 3.5-fold increased risk of cardiovascular drug use (OR(95% CI) = 3.5 [3.2-3.8]) compared to controls. Differences in cardiovascular drug use were noted as early as 7 years before the start of OHA therapy, distinguishing cases from controls. Our finding that patients with type 2 diabetes mellitus were more likely to receive treatment for cardiovascular disease several years before they start diabetes therapy supports the hypothesis of a common underlying mechanism of these two disorders and stresses the importance of the pre-diabetic state.