Article Summary A Systematic Review of Adherence With Medications for Diabetes. Cramer JA. Diabetes Care. 2004;27:1218-1224. Objective: To evaluate the degree of noncompliance and lack of persistency with oral hypoglycemic agents (OHAs) and insulin therapy, and to examine a link between these compliance issues and glycemic control. Methods: A systematic literature search was conducted using several databases to identify articles that included adherence or persistence data. Three screening processes eliminated articles and abstracts that did not meet inclusion criteria: dosing regimens and treatment adherence or persistency rates; reports of study design; and methods for assessing adherence (eg, self-report, provider estimates, medication tablet count and refill, electronic monitoring). Keywords for the literature search included "patient adherence" and "patient compliance" cross-linked with "diabetes mellitus," "hypoglycemic agents," and "insulin." The search resulted in 20 publications that met inclusion criteria. Observations: In 11 of the retrospective studies, adherence rates ranged from 36% to 93%. The mean age of study participants was >50 years, which indicated type 2 diabetes in most study patients. In an additional 5 open observational studies, the range of adherence was 79% to 85% for OHAs. Adherence to monotherapy was higher than combination treatment, at 49% vs 36%, respectively. Seven publications reported that persistency with OHA treatment ranged from 16% to 80% of patients remaining on treatment for 6 to 24 months. Adherence rates were lower in patients using insulin therapy; however, a 10-year follow-up of a large cohort of insulin-naïve patients found that 80% persisted with treatment for 24 months. Fewer patients in insulin-only groups discontinued recommended therapy compared with patients taking OHAs (20% vs 31%, respectively). Conclusion: Overall, this review confirms that many patients with diabetes do not adhere consistently to recommended therapy or are not completely persistent with regimens. Adherence rates do not appear to be related to the simplicity of a particular regimen, to the severity of disease, or to possible consequential health risks. Improved patient and provider education is necessary to increase patient compliance, adherence, and treatment persistency.