PHARMACOEPIDEMIOLOGYAND PRESCRIPTION Risk of hip fracture among older people using anxiolytic and hypnotic drugs: a nationwide prospective cohort study

Purpose Anxiolytics and hypnotics are widely used and may cause injurious falls. We aimed to examine associations between exposure to anxiolytics and hypnotics and the risk of hip fracture among all older people in Norway. Further, we wanted to examine associations between exposure to hypnotics and time of fracture. Methods A nationwide prospective cohort study of people in Norway born before 1945 (n=906,422) was conducted. We obtained information on all prescriptions of anxiolytics and hypnotics dispensed in 2004–2010 (the Norwegian Prescription Database) and all primary hip fractures in 2005–2010 (the Norwegian Hip Fracture Registry). We compared the incidence rates of hip fracture during drug exposure and non-exposure by calculating the standardized incidence ratio (SIR). Results Altogether, 39,938 people (4.4 %) experienced a primary hip fracture. The risk of hip fracture was increased for people exposed to anxiolytics (SIR 1.4, 95 % confidence interval (CI) 1.4–1.5) and hypnotics (SIR 1.2, 95 % CI 1.1– 1.2); the excess risk was highest regarding short-acting benzodiazepine anxiolytics (SIR 1.5, 95 % CI 1.4–1.6). Benzodiazepine-like hypnotics (z-hypnotics) were associated with higher excess risk of hip fracture at night (SIR 1.3, 95 % CI 1.2–1.4) than during the day (SIR 1.1, 95 % CI 1.1–1.2). Conclusions Older people had an increased risk of hip fracture during anxiolytic or hypnotic drug use, including shortacting benzodiazepine anxiolytics and z-hypnotics that were previously considered less harmful; cautious prescribing is therefore needed. People using z-hypnotics were at greatest excess risk at night; this association deserves further investigation.