title: Prevalence of unplanned hospitalizations caused by adverse drug reactions in older veterans.
abstract: OBJECTIVE
  To describe the prevalence of unplanned hospitalizations caused by adverse drug reactions (ADRs) in older veterans and to examine the association between this outcome and polypharmacy after controlling for comorbidities and other patient characteristics.
  
  
  METHODS
  Retrospective cohort.
  
  
  METHODS
  Veterans Affairs Medical Centers.
  
  
  METHODS
  Six hundred seventy-eight randomly selected unplanned hospitalizations of older (aged ≥ 65) veterans between October 1, 2003, and September 30, 2006.
  
  
  METHODS
  Naranjo ADR algorithm, ADR preventability, and polypharmacy (0-4, 5-8, and ≥9 scheduled medications).
  
  
  RESULTS
  Seventy ADRs involving 113 drugs were found in 68 (10%) hospitalizations of older veterans, of which 25 (36.8%) were preventable. Extrapolating to the population of more than 2.4 million older veterans receiving care during the study period, 8,000 hospitalizations may have been unnecessary. The most common ADRs that occurred were bradycardia (n = 6; beta-blockers, digoxin), hypoglycemia (n = 6; sulfonylureas, insulin), falls (n = 6; antidepressants, angiotensin-converting enzyme inhibitors), and mental status changes (n = 6; anticonvulsants, benzodiazepines). Overall, 44.8% of veterans took nine or more outpatient medications and 35.4% took five to eight. Using multivariable logistic regression and controlling for demographic, health-status, and access-to-care variables, polypharmacy (≥9 and 5-8) was associated with greater risk of ADR-related hospitalization (adjusted odds ratio (AOR) = 3.90, 95% confidence interval (CI) = 1.43-10.61 and AOR = 2.85, 95% CI = 1.03-7.85, respectively).
  
  
  CONCLUSIONS
  ADRs, determined using a validated causality algorithm, are a common cause of unplanned hospitalization in older veterans, are frequently preventable, and are associated with polypharmacy.
authors.affiliation: Departments of Geriatrics, School of Pharmacy, University of Pittsburgh, Pittsburgh, PA 15213, USA. zam12@pitt.edu
authors.forename: Zachary A
authors.initials: ZA
authors.lastname: Marcum
authors.forename: Megan E
authors.initials: ME
authors.lastname: Amuan
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Hanlon
authors.forename: Sherrie L
authors.initials: SL
authors.lastname: Aspinall
authors.forename: Steven M
authors.initials: SM
authors.lastname: Handler
authors.forename: Christine M
authors.initials: CM
authors.lastname: Ruby
authors.forename: Mary Jo V
authors.initials: MJ
authors.lastname: Pugh
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016001:Confidence Intervals; D064420:Drug-Related Side Effects and Adverse Reactions / Q000139:chemically induced / Q000453:epidemiology* / Q000628:therapy; D005260:Female; D005500:Follow-Up Studies; D015577:Geriatric Assessment / Q000379:methods*; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D016017:Odds Ratio; D015995:Prevalence; D012189:Retrospective Studies; D012307:Risk Factors; D014481:United States / Q000453:epidemiology; D014728:Veterans