Potential impact of benzodiazepine use on the rate of hip fractures in Denmark (DK), the Netherlands (NL) and Norway (NO)

Background: Benzodiazepines can increase the risk of falls and have therefore often been associated with an increased risk of hip fractures. However, estimations of the potential impact of benzodiazepine use on the population rate of hip fractures are missing. Objectives: To estimate the possible population impact of the use of benzodiazepines on the rate of hip fractures in DK, NL and NO. The study is part of the IMI PROTECT study and is also conducted to test the suitability of publicly available databases for drug utilization research. Methods: We conducted a literature review to estimate the pooled relative risk (RR) for hip fractures and current use of benzodiazepines. Prevalence year rates (Pe) were calculated by dividing number of ever-users of benzodiazepines in one year by the total population. The numbers of users were obtained from publicly available databases of three countries: the Register of Medicinal of Product Statistics of the Danish Medicines Agency (2007), the Dutch GIP databank (2008) and the Norwegian Prescription Database (2008). Both the RR and Pe were used for calculation of population attributable risks (PAR) of hip fractures associated with benzodiazepine use. Results: An increased risk of hip fractures was found in benzodiazepine users (RR 1.4; 95% CI 1.2-1.6). Prevalence rates of benzodiazepine use showed small differences between countries; 10.7% (DK), 13.2% (NL) and 14.5% (NO). This is reflected in results of the PARs; estimated attribution of benzodiazepines to the risk of hip fractures was 4.1% (95% CI 2.5-5.9) in DK, 5.0% (95% CI 3.1- 7.1) in NL and 5.5% (95% CI 3.4-7.8) in NO. Conclusions: This study shows that it is possible to estimate Pes and PARs using data from the three public databases. The PAR estimates suggest that the potential attribution of benzodiazepine use on the population rate of hip fractures in the three EU countries varies between 4.1% and 5.5%.