The results of this study show that individual ambulatory care expenditures for patients with T2DM increased moderately and progressively from 2005 to 2010. Increase rates were lower for patients with T2DM in a stable treatment stage (< 15%), than for controls without diabetes (26%) with an average annual rate (from 0.9% for TT to 2.8% for DT) close to the inflation rate (from 1.5% to 2.8%) over the same period (except 2009). The introduction of new classes of antidiabetic drugs in 2008-2009 (DPP4 and GLP-1 analogs) did not appear to have any substantial impact on overall health care expenditures for DM patients over the considered period. In addition, individual yearly ambulatory care expenditures increased with treatment escalation. Insulin therapy was associated with substantial cost increase compared to earlier stages of treatment, related to pharmacy but also nursing care and medical devices utilisation. Additional drug costs attributable to diabetes are not only related to antidiabetic drugs and insulin but also to other drugs, mainly cardiovascular system and psychotropic drugs (antidepressants and analgesics). Although adjustments for patient socio-demographics and co-treatments were used, it cannot be ruled out that a residual part of the estimated difference in expenditures between insulin-treated patients and other DM patients is attributable to worsening health status. However, a large part of those additional expenditures appears to be directly related to administration of insulin, as suggested by high rates of increase in costs of nursing care and medical devices.
In addition, individual yearly expenditures for DM patients with DRF were showed to exceed expenditures for other DM patients by +12% (TT) to +53% (IT), again with substantial nursing care and medical device costs for patients treated with insulin.
The estimated expenditures reported here are consistent with results of previous studies on the costs of diabetes in France. Ambulatory care expenditures were approximately €3,400 in 2007, among patients with or without insulin, compared to €3,300 (excluding hospitalisation) in ENTRED. The pharmacy expenditures estimates (€1,156, €1,411 and €1,798 in MT, DT and TT) are also comparable to those from the ENTRED study (around €1,400) . A review on costs of diabetes in France suggested that costs in patients with insulin are about twice as much as in patients treated with oral antidiabetics, which is also consistent with our findings . However, the cost difference between patients with and without insulin was thought to be largely attributable to complications . In addition, the importance of nursing care costs in patients with insulin is corroborated by a recent French publication focusing on the costs associated with insulin therapy : nursing care (€25.8/week) was the most important contributor to the costs of insulin-therapy (€45.4/week).
Real-world healthcare expenditures were measured in this study by analyzing health insurance claims data. The strengths of the EGB database, relative to other health insurance databases in Western countries, include its size, its representativity, the absence of selection according to clinical or socioeconomic criteria, and the fact that most persons are continuously enrolled. However, this study has limitations related to the utilisation of administrative data, rather than clinical data. Thus, the identification of patients with DRF was based on very restrictive assumptions. We estimated the proportion of patients with DRF at 10%, whereas higher estimates have been reported [10, 11]. This implies that the groups of patients with NRF probably included a few patients with DRF.
The EGB database contains no other socio-demographic data than age, sex, date of death, residence department and the affiliation in the CMU. Education level, income level or occupational category of beneficiaries, for which the influence on health care consumption has been demonstrated [12, 13], are absent from the EGB. This information should be collected through specific surveys.
The description of the results over time does not consider all treated DM patients but only focuses on the subpopulation of DM patients that are stable in their treatment. Patients not stable or switching from a treatment to another within the year were excluded from the analysis. This facilitated the comparison of expenditures between treatment stages but also introduced a selection bias that might affect the description of expenditures for the overall population. In particular, expenditures of switching between different treatment stages were not captured. The reported estimations are therefore conservative, reflecting the most stable and compliant patients.
Some patients in a stable treatment phase were not identified in 2010, as suggested by patient numbers by year. The selection method was based on restrictive criteria and the absence of data after December 2010 led to exclude several patients, classified as lost to follow-up.