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Mezuk B, Morden NE, Ganoczy D, Post EP, Kilbourne AM. Anticonvulsant use, bipolar disorder, and risk of fracture among older adults in the Veterans Health Administration. The American journal of geriatric psychiatry : official journal of the American Association for Geriatric Psychiatry. 2010 Mar 1; 18(3):245-55.
OBJECTIVES: To investigate the association between anticonvulsant use and fracture risk among older patients, including those with bipolar disorder (BD), an indicated condition for treatment with this class of medications. DESIGN: A prospective cohort study with 4.5 years of follow-up analyzed using both Cox proportional hazards modeling and propensity score techniques. SETTING: National sample selected from Veterans Health Administration records. PARTICIPANTS: A representative sample of 67,387 Veterans Administration patients aged 50 years and older selected in fiscal year 2002 and followed until 2006, including 29,029 with a diagnosis of BD identified from the Veterans Administration National Psychosis Registry. Pharmacy records identified 19,635 patients who had ever used anticonvulsant medications. MEASUREMENTS: Incident fracture at any site and incident hip fracture indicated by administrative data. RESULTS: There were 4,367 fractures over the 4.5-year study period. Approximately two-thirds of patients with BD were prescribed anticonvulsants, and diagnosis of BD was associated with 20% increased risk of fracture independent of anticonvulsant use. Cumulative incidence of fracture was higher among anticonvulsant users relative to never users (35.7 per 1,000 versus 14.2 per 1,000 person-years). In fully adjusted models, anticonvulsant use was associated with over twofold greater risk of fracture (hazard ratio: 2.42, 95% confidence interval: 2.23-2.633). Current use was associated with the greater risk of fracture relative to former use. Duration of anticonvulsant use was significantly associated with increased fracture risk in a graded, nonlinear manner. CONCLUSIONS: Use of anticonvulsants is associated with increased risk of fracture among older patients with BD and among those without serious mental illness.