title: Potentially Inappropriate Medication and Health Care Outcomes: An Instrumental Variable Approach.
abstract: To examine the effects of potentially inappropriate medication (PIM) use on health care outcomes in elderly individuals using an instrumental variable (IV) approach.
  
  
  
  Representative claim data from the universal health insurance program in Taiwan from 2007 to 2010.
  
  
  
  We employed a panel study design to examine the relationship between PIM and hospitalization. We applied both the naive generalized estimating equation (GEE) model, which controlled for the observed patient and hospital characteristics, and the two-stage residual inclusion (2SRI) GEE model, which further accounted for the unobserved confounding factors. The PIM prescription rate of the physician most frequently visited by each patient was used as the IV.
  
  
  
  The naive GEE models indicated that patient PIM use was associated with a higher likelihood of hospitalization (odds ratio [OR], 1.399; 95 percent confidence interval [CI], 1.363-1.435). Using the physician PIM prescribing rate as an IV, we identified a stronger significant association between PIM and hospitalization (OR, 1.990; 95 percent CI, 1.647-2.403).
  
  
  
  PIM use is associated with increased hospitalization in elderly individuals. Adjusting for unobserved confounders is needed to obtain unbiased estimates of the relationship between PIM and health care outcomes.
authors.affiliation: Institute of Health Policy and Management, College of Public Health, National Taiwan University, Taipei, Taiwan.
authors.forename: Chi-Chen
authors.initials: CC
authors.lastname: Chen
authors.affiliation: Department of Public Health, College of Medicine, Fu Jen Catholic University, Taiwan.
authors.forename: Shou-Hsia
authors.initials: SH
authors.lastname: Cheng
mesh_terms: D016208:Databases, Factual; D006304:Health Status; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D008137:Longitudinal Studies; D017063:Outcome Assessment, Health Care / Q000706:statistics & numerical data*; D000067561:Potentially Inappropriate Medication List / Q000706:statistics & numerical data*; D010818:Practice Patterns, Physicians' / Q000706:statistics & numerical data; D013624:Taiwan
keywords: Potentially inappropriate medication; health care outcomes; hospitalization; instrumental variable approach