Determination of factors affecting medication adherence in type 2 diabetes mellitus patients using a nationwide claim-based database in Japan

BACKGROUND: The extent of medication adherence in patients with type 2 diabetes mellitus (T2DM) several years after starting treatment with hypoglycemic agents remains unknown. Most previous work on medication adherence targeting this group of patients has been undertaken across a single year or is questionnaire based. This study aimed to determine medication adherence status and factors affecting adherence 3 years after initiation of hypoglycemic agents, using a nationwide medical claim-based database in Japan. METHODS: This retrospective study was conducted on data from 884 subjects with T2DM to better understand medication adherence, the effects of polypharmacy, and other factors. We also investigated the effects of medication nonadherence on hemoglobin A1c levels. Proportion of days covered was defined as the number of days for which a hypoglycemic agent was prescribed and in the patient’s possession to the number of days in the observation period. A proportion of days covered ≥0.8 were considered adherent, and those with a value <0.8 as nonadherence. Polypharmacy was defined as taking ≥5 medications. RESULTS: Of the 884 patients investigated, 440 were considered adherent during the study period. Significant factors related to adherence included number of medications (3 or 4, or ≥5), male sex, age 50–<60 years, and total number of visits ≥17. Medication adherence was also a factor related to patients with hemoglobin A1c values < 7.0% at the end of the observation period. CONCLUSIONS: We surveyed medication adherence for 3 years with post medication initiation, and found that subjects aged 50–<60 years, those with ≥3 concomitant medications, and those with a total number of visits ≥17 were more likely to be adherent and persistent, and more likely to continue their hypoglycemic agents. A high degree of medication adherence was found to have a positive influence on hemoglobin A1c levels.