Exploring unexplained twofold differences in sales of cardiovascular drugs between two neighbouring Swedish municipalities

Purpose: To analyse sales data for cardiovascular drugs and to explore the long-standing unexplained inter-municipality differences in out-patient sales, especially for ACE inhibitors/angiotensin II antagonists (ATC-group C09) and statins (C10AA) between two Swedish neighbouring municipalities.

Methods: Crude and age-standardised data regarding drug sales on prescription from the National Corporation of Swedish Pharmacies, was analysed. In subsequent qualitative interviews, the sales data were presented to a number of purposefully chosen key persons exploring their explanations of the long-standing large differences in the sales between the two neighbouring municipalities.

Results: The study confirms previous analyses that large inter-municipality differences in out-patient sales of cardiovascular drugs exist between the municipalities, differences that remained when data were standardised. In the year 2002, for example, the age-standardised out-patient sales of drugs in ATC-group C09 was 64.4 defined daily dose (DDD)/1000 inhabitants/day in one municipality compared to 112.1 in the other. For ATC-group C10AA, the corresponding figures were 41.7 and 80.9 respectively. All interviewees considered so called treatment traditions as the most important reason for the observed differences. Taking part in clinical trials was also believed to be of great importance. Activities of the Drug and Therapeutic Committees (DTC), the presence of a hospital in the municipality, marketing activities by pharmaceutical companies or differences in morbidity were not considered of major importance in explaining the differences.

Conclusions: Large differences in sales data between the two municipalities remained despite age and sex standardisation. Key informants shared the view that differences in the so called 'treatment traditions' were most important for the differences.