Prevalence, Total and Excess Costs of Diabetes and Related Complications in Ontario, Canada

BACKGROUND: Diabetes costing studies often do not identify the marginal costs directly attributable to the disease. The objective of this study is to estimate the prevalence, total and excess costs attributable to diabetes and its complications in Ontario over 11 years ( 1995 to 2005). METHODS: Incident type 1 and type 2 diabetes cases, with and without the following complications, were identified from the Ontario Diabetes Database: myocardial infarction, stroke, angina, heart failure, blindness in 1 eye, amputation, nephropathy and cataracts. Patients were matched 2: 1 with controls. Excess costs of diabetes were estimated as the difference between costs attributed to patients with diabetes vs. those attributed to patients without diabetes. Another control group consisting of all patients in Ontario older than 35 years was used to compare the cost of complications for patients with and without diabetes. RESULTS: The prevalence of diabetes rose drastically, from 6.5 to 10.5%. Excess costs were $2930 in the year of diabetes diagnosis and $1240 in subsequent years. In the year of the event, cost differences were greatest for patients with diabetes who had an amputation ($5133), followed closely by nephropathy ($4117) and stroke cases ($3965). CONCLUSIONS: Findings from this study illustrate that the prevalence of diabetes has almost doubled between 1995 and 2005; that researchers can overestimate total costs if excess costs directly attributable to diabetes are not considered; and that they can underestimate total costs if disease-specific complication costs are not considered.