Poor adherence to prescribed medication regimens is a recognized challenge in many disease states. For example, low adherence rates to cardiovascular medications have been associated with an increased risk of hospitalization and mortality in patients with coronary artery disease and congestive heart failure. Observational studies demonstrate that adherence to oral antidiabetic drugs appears to be highest during the initial management stages of type 2 diabetes, but tapers as duration of disease increases. Although poor adherence to oral antidiabetic drugs has been associated with poor metabolic control in some patient groups, the impact of poor adherence on clinical outcomes is less well known.

This study is designed to evaluate the relationship between medication adherence and important clinical outcomes such as secondary failure (the need to add to or switch initial therapy due to loss of metabolic control), hospitalization, and mortality. Data from the cohort of 12,272 new users of oral antidiabetic drugs, identified for the Metformin and Clinical Outcomes project, will be used for this study. Adherence to oral antidiabetic drugs will be estimated as a daily dose calculated using available data from the Saskatchewan Prescription Drug Plan database. We postulate that subjects with higher adherence rates will have a lower risk of clinical events compared to subjects with lower adherence rates. We will also test the hypothesis that higher adherence rates are associated with a delay in the time to clinical events.

Research Team

Jeff Johnson, Scot Simpson, Sumit Majumdar, Ross Tsuyuki


Institute of Health Economics


Simpson SH, Eurich DT, Majumdar SR, Padwal RS, Tsuyuki RT, Varney J. Johnson JA. A Meta-Analysis of the Relationship Between Drug Therapy Adherence and Mortality. British Medical Journal 2006 Jul 1;333(7557):15.

Simpson SH, Majumdar SR, Tsuyuki RT, Eurich DT, Johnson JA. Dose-response relationship between sulfonylureas and mortality in type 2 diabetes: a population-based cohort study. Canadian Medical Association Journal 2006;174:169-174.