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 830.90euros in diabetic patients and 182.80euros 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.