Joshua M Thorpe, Carolyn T Thorpe, Walid F Gellad, Chester B Good, Joseph T Hanlon, Maria K Mor, John R Pleis, Loren J Schleiden, Courtney Harold Van Houtven

Recent federal policy changes attempt to expand veterans' access to providers outside the Department of Veterans Affairs (VA). Receipt of prescription medications across unconnected systems of care may increase the risk for unsafe prescribing, particularly in persons with dementia. To investigate the association between dual health care system use and potentially unsafe medication (PUM) prescribing. Retrospective cohort study. National VA outpatient care facilities in 2010. 75 829 veterans with dementia who were continuously enrolled in Medicare from 2007 to 2010; 80% were VA-only users, and 20% were VA-Medicare Part D (dual) users. Augmented inverse propensity weighting was used to estimate the effect of dual-system versus VA-only prescribing on 4 indicators of PUM prescribing in 2010: any exposure to Healthcare Effectiveness Data and Information Set (HEDIS) high-risk medication in older adults (PUM-HEDIS), any daily exposure to prescriptions with a cumulative Anticholinergic Cognitive Burden (ACB) score of 3 or higher (PUM-ACB), any antipsychotic prescription (PUM-antipsychotic), and any PUM exposure (any-PUM). The annual number of days of each PUM exposure was also examined. Compared with VA-only users, dual users had more than double the odds of exposure to any-PUM (odds ratio [OR], 2.2 [95% CI, 2.2 to 2.3]), PUM-HEDIS (OR, 2.4 [CI, 2.2 to 2.8]), and PUM-ACB (OR, 2.1 [CI, 2.0 to 2.2]). The odds of PUM-antipsychotic exposure were also greater in dual users (OR, 1.5 [CI, 1.4 to 1.6]). Dual users had an adjusted average of 44.1 additional days of any-PUM exposure (CI, 37.2 to 45.0 days). Observational study design of veteran outpatients only. Among veterans with dementia, rates of PUM prescribing are significantly higher among dual-system users than with VA-only users. U.S. Department of Veterans Affairs.