Health Care Costs in People With Diabetes and Their Association With Glycemic Control and Kidney Function

OBJECTIVE: To determine the association between laboratory-derived measures of glycemic control (HbA(1c)) and the presence of renal complications (measured by proteinuria and estimated glomerular filtration rate [eGFR]) with the 5-year costs of caring for people with diabetes. RESEARCH DESIGN AND METHODS: We estimated the cumulative 5-year cost of caring for people with diabetes using a province-wide cohort of adults with diabetes as of 1 May 2004. Costs included physician visits, hospitalizations, ambulatory care (emergency room visits, day surgery, and day medicine), and drug costs for people >65 years of age. Using linked laboratory and administrative clinical and costing data, we determined the association between baseline glycemic control (HbA(1c)), proteinuria, and kidney function (eGFR) and 5-year costs, controlling for age, socioeconomic status, duration of diabetes, and comorbid illness. RESULTS: We identified 138,662 adults with diabetes. The mean 5-year cost of diabetes in the overall cohort was $26,978 per patient, excluding drug costs. The mean 5-year cost for the subset of people >65 years of age, including drug costs, was $44,511 (Canadian dollars). Cost increased with worsening kidney function, presence of proteinuria, and suboptimal glycemic control (HbA(1c) >7.9%). Increasing age, Aboriginal status, socioeconomic status, duration of diabetes, and comorbid illness were also associated with increasing cost. CONCLUSIONS: The cost of caring for people with diabetes is substantial and is associated with suboptimal glycemic control, abnormal kidney function, and proteinuria. Future studies should assess if improvements in the management of diabetes, assessed with laboratory-derived measurements, result in cost reductions.