Different study criteria affect the prevalence of benzodiazepine use.

Background: Different prevalences of benzodiazepine (BZ) use are described in the literature. The present study assessed the effects of employing various definitions of BZ use and various observation periods on the prevalence rate of BZ use in an open population aged 18-74 years.
Method: In a literature review, prevalence studies were systematically compared. In a second stage, a descriptive cross-sectional multipractice study was analysed using 48,046 prescriptions of BZ in the past year given to a population of 80,315 patients at 31 general practices in the Nijmegen Health Area. From this database, prevalence rates were calculated applying different definitions of BZ use and different observation periods.
Results: In the literature, prevalence rates varied between 2.2 and 17.6%. There was wide variation in definitions of BZ use and observation period. In our prescription database, depending on the definitions of BZ use and observation period, prevalence rates ranged from 0.2% to 8.9%. The ratio of female:male (2:1) remained constant irrespective of the prevalence rate. Age distribution varied according to the duration of use: among long-term BZ users, approximately 80% were older than 45 years; among short-term BZ users, approximately 55% were older than 45 years.
Conclusions: The wide variation in prevalence rates of BZ use reported in the literature can largely be explained by differences in definitions of BZ use and observation period. This affected the distribution of some BZ-use-related variables such as age. For reliable comparisons of BZ use, standardisation of the definition of BZ use is required. A proposal for standardising methodology is presented.