Factors associated with adherence to oral antihyperglycemic monotherapy in patients with type 2 diabetes

AIM: To estimate the rate of adherence to oral antihyperglycemic monotherapy for patients with type 2 diabetes in the US and describe factors associated with adherence in these patients. MATERIALS AND METHODS: In this retrospective cohort analysis, patients aged 18 years or older with a type 2 diabetes diagnosis received between 1 January 2007 and 31 March 2010 were identified using a large US-based health care claims database. The index date was defined as the date of the first prescription for oral antihyperglycemic monotherapy during this period. Patients had to have continuous enrollment in the claims database for 12 months before and after the index date. Adherence was assessed using proportion of days covered (PDC) and an adjusted logistic regression analysis was performed to evaluate factors associated with adherence (PDC ≥80%). RESULTS: Of the 133,449 eligible patients, the mean age was 61 years and 51% were men. Mean PDC was 75% and the proportion of patients adherent to oral antihyperglycemic monotherapy was 59%. Both mean PDC and PDC ≥80% increased with increasing age and the number of concomitant medications, and were slightly higher in men compared to women. Results from the logistic regression demonstrate an increased likelihood of non-adherence for patients who were younger, new to therapy, on a twice-daily dose, female, or on fewer than three concomitant medications compared to their reference groups. Higher average daily out-of-pocket pharmacy expense was also associated with an increased likelihood of non-adherence. All results were statistically significant (P<0.05). CONCLUSION: Patient characteristics, treatment regimens, and out-of-pocket expenses were associated with adherence to oral antihyperglycemic monotherapy in our study.