Antiepileptic drug use in seven electronic health record databases in Europe: a methodological comparison.

Background: The annual prevalence of antiepileptic drug (AED) prescribing reported in the literature differs considerably among European countries; this may be due to differences in type of data sources, time periods, population distributions, and methodology. Objectives: To assess the prevalence of AED prescribing across seven European routine health care databases in Spain, Denmark, the Netherlands, the UK, and Germany using standardised methodology and to investigate sources of variation. Methods: We used data from the Spanish Base de Datos para la Investigacion Farmacoepidemiologica en Atencion Primaria (BIFAP), the Danish national registries, the Dutch Mondriaan project (AHC, NPCRD), The Health Improvement Network (THIN) and the Clinical Practice Research Datalink (CPRD) from the UK, and the German Bavarian claims database (KVB). Analyses on annual prevalence of AEDs over the study period of 2001–2009 were stratified by sex, age, and AED type (‘old’ vs. ‘new’ depending registration year for marketing). Overall prevalences were standardised to the European 2008 reference population. Results: Prevalence of any AED varied from 79 per 10,000 persons in the Netherlands to 147 per 10,000 persons in Spain in 2001. After standardisation this range decreased to 88 per 10,000 persons in the Netherlands to 144 per 10,000 in Spain and Denmark. In all databases prevalence increased yearly since 2001 with 6% in Denmark to 15% in Spain. This increase could be entirely attributed to an increase in prescribing of ‘new’ AEDs. AED use increased with age for both females and males up to ages of 80–89 years-old and tended to be somewhat higher in females between 40 and 70 years-old. We did not find differences across databases in the number of AEDs concomitantly used. Conclusions: During the study period of 2001–2009, AED prescribing increased in all five EU countries which was mainly due to newer AEDs. Using a standardised methodology showed consistent trends across databases and countries over time. Differences in age and sex distribution explained part of the variation between countries