AGE STANDARDIZATION OF DRUG UTILIZATION - COMPARISONS OF DIFFERENT METHODS USING CARDIOVASCULAR DRUG DATA FROM SWEDEN AND SPAIN

In drug utilisation studies, the units of defined daily doses (DDD) an d DDD/1000 inhabitants per day standardise for differences in dosage a nd population size, but not for age-related differences in drug utilis ation. There is no consensus as to how age standardisation of DDD data should be carried out. Using cardiovascular drug utilisation data fro m Sweden and Spain, the current study compared the outcome of differen t methods of age standardisation. Both indirect methods (based on a co mparison of observed and expected drug usage) and direct methods (usin g different weighting for the age categories) were used. The largest i mpact of standardisation was seen for diuretics. The crude rate for me n and women combined was 26 DDD/1000 inhabitants per day in Costa de P onent and 98 DDD/1000 inhabitants per day in Varmland. The correspondi ng figures when standardising the Costa de Ponent population were 26 a nd 58, respectively. Using the equivalent average rate (EAR) method, t he rate for Varmland was 129 DDD/1000 inhabitants per day. Lesser but still important differences were found for beta-adrenoceptor and antih ypertensives. Thus, the results of standardisation differ depending on which method is used and which drugs are evaluated. EAR is recommende d for direct standardisation because of its ease of use and because it does not require the choice of a standard population.