Impact of nonadherence on complication risks and healthcare costs in patients newly-diagnosed with diabetes.

AIMS: To investigate the association between nonadherence to diabetes treatment and the occurrence of diabetes complications.

METHODS: Our study retrospectively identified adherence and nonadherence to diabetes treatment in patients during the first year of observation after new diagnoses of type 2 diabetes enrolled in commercial database from 52 health insurers in Japan. Participants were insurance enrollees with type 2 diabetes who received healthcare between 2005 and 2013, and who could be tracked for more than 12months from the initiation of diabetes treatment. We compared the occurrence of diabetes-related complications (retinopathy, nephropathy, neuropathy, ischemic heart disease, cerebrovascular disease, and chronic arterial occlusion) and all-cause healthcare expenditure during the second to eighth years.

RESULTS: We identified 1784 nonadherent patients and 9547 adherent patients. Cox proportional hazard models showed that the occurrence of microvascular complications was significantly higher in the nonadherent group: the hazard ratios (95% confidence intervals) for retinopathy, nephropathy, and neuropathy were 2.04 (1.57-2.66), 1.91 (1.35-2.72), and 1.83 (1.02-3.27), respectively. However, no significant differences were observed between the adherent and nonadherent groups for the macrovascular complications (ischemic heart disease, cerebrovascular disease, and chronic arterial occlusion). In addition, the nonadherent group had a significantly higher cumulative healthcare expenditure than the adherent group during the second-to-fifth-year period (p=0.029) and the second-to-sixth-year period (p=0.009) after treatment initiation.

CONCLUSIONS: Nonadherence in the first year of diabetes may increase the incidence of complications and result in higher expenditures for patients and payers.