Increased risk of hip fracture among older people using antidepressant drugs: data from the Norwegian Prescription Database and the Norwegian Hip Fracture Registry

Background: hip fractures are usually caused by a combination of reduced bone mineral density and falls; using antidepressant drugs may affect both of these. Objective: we aimed to examine associations between exposure to antidepressant drugs and the risk of hip fracture among older people, and, provided associations found, to estimate the attributable risk of hip fracture. Design: we conducted a nationwide prospective cohort study of the 906,422 people in Norway born before 1945. Methods: information on all prescriptions of antidepressants dispensed in 2004-10 and all primary hip fractures in 2005-10 was obtained from the Norwegian Prescription Database, and the Norwegian Hip Fracture Registry, respectively. The incidence rates of hip fracture during the time people were exposed and unexposed to antidepressant drugs were compared by calculating the standardised 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 any antidepressant [SIR = 1.7, 95% confidence interval (CI) 1.7-1.8]; tricyclic antidepressants (SIR = 1.4, 95% CI: 1.3-1.5); selective serotonin reuptake inhibitors (SSRIs) (SIR = 1.8, 95% CI: 1.7-1.8) and other antidepressants (SIR = 1.6, 95% CI: 1.5-1.7). The risk of hip fracture attributable to exposure to antidepressant drugs was 4.7%. Conclusions: this study indicated an increased risk of hip fracture among people exposed to antidepressants, especially those with serotonergic properties such as SSRIs. This association needs to be explored further in clinical studies.