Cumulative cost of prescription medication in outpatients with type 1 diabetes in Finland.

AIMS/HYPOTHESIS: We examined the 11-year cumulative outpatient cost of prescription medication in patients with type 1 diabetes by subgroups according to the presence of complications and duration of diabetes.

METHODS

This longitudinal study included a nationally representative cohort of patients with type 1 diabetes (N = 3,717) from the Finnish Diabetic Nephropathy Study (FinnDiane). The data were linked to the Drug Prescription Register. The cumulative cost was calculated between 1998 and 2008. Information on complications was updated until 2008. Patients were divided into 10-year groups according to the duration of diabetes in 1998. Generalised linear mixed models under gamma distribution were used to evaluate the costs.

RESULTS

Approximately 25% of the patients had macrovascular disease (MVD) and/or end-stage renal disease (ESRD). The adjusted cumulative cost of medications increased 56% when MVD was present compared with those without complications. In patients with ESRD or with both complications present the cost increased fourfold or 15-fold, respectively, when diabetes medications were excluded. The proportion of renal failure related medications (immunosuppressants, peritoneal dialytics and erythropoietin) accounted for more than 70% of these costs. The cost of diabetes medication was rather stable, irrespective of complication status or duration of diabetes. However, when complications were present these costs were markedly lower in all 10-year duration groups.

CONCLUSIONS/INTERPRETATION: This study shows that ESRD has a great impact on outpatient prescription medication costs. Since no considerable differences were observed in the cost of diabetes medication, the increase was completely due to the cost of medications related to comorbidity.