The impact of diabetes on prescription drug costs: the population-based Turin study

Aims/hypothesis The aim of our study was to compare prescription drug costs in diabetic and non-diabetic individuals in a large population-based Italian cohort covered by the National Health System. Methods We identified diabetic residents in Turin on 31 July 2003 through multiple independent data sources (diabetes registry, hospital discharges and prescriptions data sources). All prescriptions registered in the 12 month period 1 August 2003 to 31 July 2004 were examined to compare prevalence of treatment and costs in diabetic (n=33,797) and non-diabetic individuals (n=863,876). A log-linear model was employed to estimate age- and sex-adjusted ratios of costs. Results Costs per person per year were n=830.90 in diabetic patients and epsilon 182.80 in non-diabetic individuals (age- and sex-adjusted rate ratio 2.8, 95% CI 2.7-2.9). Diabetes treatment accounted for 18.5% of the total cost. Compared with non-diabetic individuals, the excess of expenditure was particularly high in diabetic patients aged < 45 years (rate ratio 9.3), in those with type 1 diabetes (rate ratio 7.7) and in insulin users (rate ratio 4.8). The cost of diet-treated patients was similar to those treated with oral drugs. Diabetes was associated with an increased prevalence of treatment for most drug categories; one-third of the diabetic cohort received ACE inhibitors, anti-thrombotic drugs and statins. Conclusions/Interpretation This population-based study shows that diabetes has a great impact on prescription drug costs, independently of main confounders, particularly in insulin-treated patients, suggesting that a wide range of comorbidities affect their health. Costs are expected to further increase if the transferability of knowledge provided by evidence-based guidelines on diabetic patients is completed over the coming years.