New evidence on benzodiazepine use and falls: the time factor.

The objectives of this prospective study were to calculate incidence rates for fall-related hospitalization, to compare the effect of risk factors among benzodiazepine (BZD) users and unexposed controls, and to examine variations in risks according to length of time following a BZD prescription. Data were derived from Saskatchewan Health linked data bases, leading to information on 468 hospitalizations for injury due to falls among a study population of 321422. Incidence rates per 10000 within 28 days of the prescription fill date were 26.2, 12.1 and 9.0 for BZD sedative users, BZD tranquillizer users and for unexposed controls, respectively. Incidence rates increased with age, and were higher for women than for men. Results from multivariate logistic regression models also showed a greater risk of falling for BZD users but the odds ratio was higher for men than for women. A history of treatment for alcohol abuse was a very strong risk factor for falls among both men (odds ratio, 10.7) and women (odds ratio, 4.3). The highest risk of serious injury due to falls was within 15 days of filling the prescription, with an odds ratio of 3.6 for BZD sedatives and 2.6 for BZD tranquillizers. Risk decreased with further increase of time after the BZD fill date. For the individual BZD, flurazepam and triazolam showed the highest increase in risk with odds ratios of 3.4 and 2.7, respectively, while oxazepam, lorazepam and diazepam showed odds ratios of 2.2, 2.0 and 1.8 (all odds ratios mentioned are statistically significant at p < 0.05).