Antipsychotic Drugs and Risk of Hip Fracture in People Aged 60 and Older in Norway

Abstract

Objectives: To examine associations between exposure to various subgroups of antipsychotic drugs and risk of hip fracture in older adults.

Design: Nationwide cohort study.

Setting: Norway, 2005-2010.

Participants: Everyone living in Norway born before 1945 (N = 906,422).

Measurements: Information was obtained on all prescriptions of antipsychotic drugs dispensed from 2004 to 2010 (Norwegian Prescription Database) and data on all primary hip fractures from 2005 to 2010 (Norwegian Hip Fracture Registry). Incidence rates of hip fracture during person-time exposed and unexposed to antipsychotic drugs were compared by calculating the standardized incidence ratio (SIR).

Results: Thirty-nine thousand nine hundred thirty-eight (4.4%) participants experienced a primary hip fracture. Greater risk of hip fracture was associated with exposure to any antipsychotic (SIR = 2.1, 95% confidence interval (CI) = 1.9-2.1), first-generation antipsychotics (SIR = 2.0, 95% CI = 1.8-2.2), second-generation antipsychotics (SIR = 2.2, 95% CI = 1.9-2.4), prolactin-sparing antipsychotics (SIR = 2.4, 95% CI = 1.8-3.1) and prolactin-elevating antipsychotics (SIR = 2.0, 95% CI = 1.9-2.2).

Conclusion: In people aged 60 and older in Norway, those who took an antipsychotic drug had twice the risk of sustaining a hip fracture during exposure than during nonexposure. Although confounding by indication, comorbidity, or other drugs used cannot be excluded, this association is relevant for clinical practice because hip fracture and antipsychotic drug use are prevalent in vulnerable older individuals. Clinical studies examining mechanisms or causality of the observed association between antipsychotic drug use and excess risk of hip fracture are needed.

Keywords: aged; antipsychotics; hip fractures; pharmacoepidemiology; population registers.