Background: There is evidence that medications used to treat diabetes mellitus improve patient outcomes. National guidelines advocate glycemic, blood pressure, and cholesterol control. Despite these recommendations, less than one half of patients with diabetes meet targets for all three components. Medication nonadherence may account for patients not meeting these goals. In one study, less than one half of patients given a new prescription for statin therapy were still taking the medication one year later. Also, nonadherence to antihypertensives and diabetes medications may be a major factor in poor control. Previous studies have not evaluated medication nonadherence and mortality outcomes. To assess this impact, Ho and colleagues evaluated the effect of medication nonadherence on all-cause mortality and all-cause hospitalizations in patients with diabetes.

The Study: The trial was a retrospective cohort study performed in an integrated health care management system of patients diagnosed with diabetes who were enrolled in the registry. All medications dispensed from the outpatient facilities to the members of this group were recorded. Medications included in the study were oral hypoglycemics, antihypertensives, and statins. Adherence to the medications was calculated by using the portion of the days covered, which was based on the total number of days supplied for filled prescriptions. Nonadherence was indicated if the patient had fewer than 80 percent of the days covered. Primary outcomes measured were all-cause hospitalization and mortality rates. Secondary outcomes included achievement of target A1C, blood pressure, and low-density lipoprotein (LDL) cholesterol levels.

Results: Of the 11,532 patients enrolled in the study, 20.4 percent had diet-controlled diabetes, 9.7 percent required insulin, 57 percent were using only hypoglycemic agents, and 13 percent were using a combination of insulin and oral hypoglycemic agents. Based on collected data, 21.3 percent (2,456 patients) were identified as nonadherent to their medication regimen. These patients were younger and had fewer comorbidities than those who were adherent. During follow-up, nonadherent patients had higher A1C, LDL cholesterol, and blood pressure levels compared with the adherent group. Additionally, patients who were nonadherent were significantly more likely to die or become hospitalized during the study than those who were adherent. The odds ratio for all-cause mortality for those who failed to take their medications as prescribed was 1.81 (95% confidence interval, 1.46 to 2.23). However, a 25 percent increase in compliance was associated with a significant reduction of all-cause mortality and hospitalizations.

Conclusion: A significant number of patients with diabetes are nonadherent to their medication regimens, which is associated with a significant increase in adverse outcomes. To improve patient adherence to diabetic medications, interventions aimed at compliance should be implemented.