Patient Cohorts and Overall Costs

Across the two health authorities we identified 304,779 people with a diagnosis of diabetes, of whom 288,097 patients were being treated with antidiabetic drugs in 2018 (Table 4). Of these 24,710 were from Umbria and 263,387 were from Campania. Amongst this total cohort, 37,333 (13.0%) were people with T1D/T2D-MDI, 36,450 (12.7%) were people with T2D-Basal and 214,314 (74.4%) were people with T2D-Oral. Average annual cost per patient across the total cohort was similar for the T1D/T2D-MDI and T2D-Basal cohorts (respectively €2580 and €2254) and significantly lower for the T2D-Oral cohort (€1145). This pattern was also reflected in the individual costs of treatment in the separate regions, with a slightly lower per-patient cost for treatment in Umbria compared to Campania (Table 4).

Table 4 Diabetes treatment groups and per-patient costs in 2018Overall Costs of Care for People with Diabetes

The costs of drug prescriptions and delivery, specialist outpatient care and hospitalizations for the cohort of people with diabetes in Umbria and Campania health authorities are summarized in Table 5 and Supplementary Table S1, along with the aggregate costs for the total patient cohort. The average treatment cost per patient in Umbria and Campania (Fig. 1) was €1229 and €1495, respectively, with higher costs for the T1D/T2D-MDI treatment groups (€2266 and €2621 respectively) or the T2D-Basal treatment groups (€1979 and €2272 respectively) compared to T2D-Oral treatment group (€891 and €1169 respectively).

Table 5 Average costs per diabetes treatment group and number of comorbidities in 2018Fig. 1

Per-person treatment costs for Umbria (a, c, e) and Campania (b, d, f). MDI multiple daily injections with insulin, Basal basal insulin, T1D type 1 diabetes, T2D type 2 diabetes

The average cost per patient increases according to the number of comorbidities (Fig. 1, Table 5, Supplementary Table S1). For the T1D/T2D-MDI treatment groups, patients in Umbria and Campania without comorbidities have treatment costs of €735 and €781, respectively, rising to €5639 and €17,922 for patients with four or more comorbidities (Fig. 1a, Fig. 1b). The T2D-Basal treatment groups had similarly low treatment costs when no comorbidities were present, rising progressively to €4154 (Umbria) and €6078 (Campania) for four or more comorbidities. The T2D-Oral group showed a similar pattern in each region, although costs did not escalate to the same level as for the T1D/T2D-MDI and T2D-Basal treatment groups. For patients with one or no comorbidities, the most significant costs are for drug prescriptions and delivery, whereas as the number of comorbidities increases the costs of hospitalizations become the most significant cost of care (Fig. 1, Table 5, Supplementary Table S1).

Distribution of Costs of Care for People with Diabetes on Different Treatment Regimens

Average treatment costs for people with diabetes increased considerably as the number of comorbidities increased (Table 6, Supplementary Table S2). Across the total cohort of patients the per-person treatment cost for those without comorbidities was €459, rising to €7464 for a person with diabetes and four or more comorbidities.

Table 6 Average treatment costs per-patient and number of comorbidities in 2018

For people in the T1D/T2D-MDI treatment group the pattern of costs was similar across Umbria and Campania regions for people with fewer than four comorbidities (Fig. 1a, b). Drug costs were most significant for people with one or no comorbidities, whereas costs for hospitalization were largest for those with two or three comorbidities. For Umbria, patients with diabetes and four or more comorbidities had hospitalization as the major cost of care, whereas the Campania region registered drug costs as being the most significant cost (63.8% of total cost) for this treatment group. However, the small number of patients with four or more comorbidities in Campania (n = 165, 0.5%) was also accompanied by a much larger per-patient cost in this cohort (€17,922), and the small number of patients in the T1D/T2D-MDI group in Umbria (n = 37, 0.9%) means that a meaningful comparison between people with four or more comorbidities is impractical.

For people in the T2D-Basal treatment group the pattern of costs was similar across Umbria and Campania regions, with progressive increases at each level of comorbidity (Fig. 1). Drug costs were most significant for people with one or no comorbidities, drug and hospital costs were equally significant for people with two comorbidities, and costs for hospitalization were largest for people with three or more comorbidities.

Treatment costs for the T1D/T2D-MDI group and the T2D-Basal group were comparable in both Umbria and Campania, with increasing costs per patient with rising numbers of comorbidity, with the exception of the T1D/T2D-MDI group in Campania, as indicated above.

Per-patient treatment costs for the T2D-Oral patient group were lower than in the two insulin-treated groups (Table 4). In this context, the overall distribution of patients amongst the treatment groups is shown in Fig. 2a, compared to the distribution of treatment costs (Fig. 2b). Cost distribution was comparable with the insulin-treated cohorts, with the emphasis on drug costs at low levels of comorbidity, with the cost of hospitalization becoming the major factor as comorbidities increased.

Fig. 2

Overall distribution of (a) patients and (b) costs per treatment group. MDI multiple daily injections with insulin, Basal basal insulin, T1D type 1 diabetes, T2D type 2 diabetes

Hospital admission for ADEs amongst the treatment groups, related to hypoglycemia, DKA, coma and hyperglycemia, was assessed according to ICD9 codes. In both regions, hospitalization for at least one ADE was significant in the T1D/T2D-MDI and T2D-Basal cohorts, with increasing prevalence at greater numbers of comorbidities (Fig. 3a–d). ADEs resulting in hospital admission were much less frequent in the T2D-Oral treatment cohort (Fig. 3e, f).

Fig. 3

(a–f) Acute diabetes events per treatment group and number of comorbidities. MDI multiple daily injections with insulin, Basal basal insulin, T1D type 1 diabetes, T2D type 2 diabetes

Modelling of Diabetes Treatment Costs in Italy

On the basis of the treatment costs available for Umbria and Campania in 2018, we modelled the total treatment costs for the population of people with diabetes in Italy (Table 7, Supplementary Table S2). The total number of people with a diagnosis of diabetes in Italy was taken to be 3,483,860, which was previously identified through linkage of the Marche healthcare authority [9]. On the basis of the data for Umbria and Campania, 79.21% of people with a diagnosis of diabetes were on antidiabetic treatment regimens in Umbria, and the corresponding proportion for Campania was 96.27%. Thus, treatment costs for Italy were modelled for 2,759,566 patients (based on Umbria) and for 3,353,912 patients (based on Campania).

Table 7 Costs of diabetes care for Italy modelled on the data from Umbria and Campania

In both scenarios, treatment costs are driven primarily by the cost of hospitalization, followed by drug costs (Table 7, Supplementary Table S2, Fig. 4). Thus, based on the model extrapolated from the Umbria data, the total direct costs for diabetes in Italy would be €3.39 billion, whereas the model populated using the Campania data would be €5.01 billion. The model based on Umbria puts the annual cost of hospitalization for all treatment groups at €1.43 billion, with €1.34 billion spent on prescription drugs. Based on the Campania data, the annual cost of hospitalization is €2.28 billion, with drug treatment costs of €2.04 billion. As with the separate data from Umbria and Campania, the proportion of costs for hospitalization in the model for Italy increases as the number of comorbidities rises.

Fig. 4

Distribution of treatment costs of diabetes for Italy modelled on data from (a) Umbria and (b) Campania