Increasing polypharmacy - an individual-based study of the Swedish population 2005-2008.

Background: An increase in the use of drugs and polypharmacy have been displayed over time in spite of the fact that polypharmacy represents a well known risk factor as regards patients' health due to the adverse drug reactions, drug-drug interactions, and low adherence to drug therapy arising from polypharmacy. For policymakers, as well as for clinicians, it is important to follow the developing trends in drug use and polypharmacy over time. We wanted to study if the prevalence of polypharmacy in an entire national population has changed during a 4-year period.

Methods: By applying individual-based data on dispensed drugs, we have studied all dispensed prescribed drugs for the entire Swedish population during four 3-month periods 2005-2008. Five or more (DP ≥5) and ten or more (DP ≥10) dispensed drugs during the 3-month period was applied as the cut-offs indicating the existence of polypharmacy and excessive polypharmacy respectively.

Results: During the period 2005-2008, the prevalence of polypharmacy (DP≥5) increased by 8.2% (from 0.102 to 0.111), and the prevalence of excessive polypharmacy (DP≥10) increased by 15.7% (from 0.021 to 0.024).In terms of age groups, the prevalence of polypharmacy and excessive polypharmacy increased as regards all ages with the exception of the age group 0-9 years. However, the prevalence of excessive polypharmacy displayed a clear age trend, with the largest increase for the groups 70 years and above. Furthermore, the increase in the prevalence of polypharmacy was, generally, approximately twice as high for men as for women. Finally, the mean number of dispensed drugs per individual increased by 3.6% (from 3.3 to 3.4) during the study period.

Conclusions: The prevalence of polypharmacy and excessive polypharmacy, as well as the mean number of dispensed drugs per individual, increased year-by-year in Sweden 2005-2008.