title: Relationships between antiparkinson medication nonadherence, regimen modifications, and healthcare utilization and expenditures.
abstract: OBJECTIVE
  To examine 1) the effect of prior antiparkinson drug (APD) nonadherence on subsequent APD regimen modifications; and 2) the influence of modifications on healthcare utilization and costs by patients with Parkinson's disease (PD).
  
  
  METHODS
  This retrospective cohort study included 7052 PD patients with ≥2 APD prescriptions who initiated a modification of APD regimens in 2007. Modification was assessed as changing from one APD to another and/or adding a new APD to an existing regimen. Nonadherence was measured using Medication Possession Ratio <0.8. Discrete-time survival analyses were used to estimate the effect of prior nonadherent behavior on initiating APD modifications. Generalized linear models were used to estimate the effect of initiating medication modifications on subsequent 3-month medical use and costs.
  
  
  RESULTS
  Initiation of APD modifications in any given month was higher among patients who were nonadherent to APDs in the preceding month (adjusted hazard ratio [HR] = 1.23), compared to their adherent counterparts. Modifications significantly predicted higher risk of all-cause and PD-related hospitalizations (adjusted relative risk [RR] = 1.22 and 1.83, respectively), home health agency utilization (RR = 1.18 and 1.52), and use of physician services (RR = 1.14 and 1.41), as well as higher total all-cause healthcare expenditures (mean = $1064) in any given 3-month interval.
  
  
  CONCLUSIONS
  Prior nonadherence to APDs might influence initiation of APD modification. APD modifications were associated with increased health care utilization and expenditures, with the caveats that indications of modifications and disease severity may still play roles. Prescribers should consider patients' medication adherence when changing APD regimens to lower the costs of medical services.
authors.affiliation: Department of Pharmaceutical Health Services Research, University of Maryland School of Pharmacy, Baltimore, MD, USA. Electronic address: ywei001@umaryland.edu.
authors.forename: Yu-Jung
authors.initials: YJ
authors.lastname: Wei
authors.affiliation: Department of Pharmaceutical Health Services Research, University of Maryland School of Pharmacy, Baltimore, MD, USA; Center on Drugs and Public Policy, University of Maryland School of Pharmacy, Baltimore, MD, USA. Electronic address: fpalumbo@rx.umaryland.edu.
authors.forename: Francis B
authors.initials: FB
authors.lastname: Palumbo
authors.affiliation: Department of Pharmaceutical Health Services Research, University of Maryland School of Pharmacy, Baltimore, MD, USA; Peter Lamy Center on Drug Therapy and Aging, University of Maryland School of Pharmacy, Baltimore, MD, USA. Electronic address: lsimoniw@rx.umaryland.edu.
authors.forename: Linda
authors.initials: L
authors.lastname: Simoni-Wastila
authors.affiliation: Department of Neurology, University of Maryland School of Medicine, Baltimore, MD, USA. Electronic address: lshulman@som.umaryland.edu.
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Shulman
authors.affiliation: Department of Pharmaceutical Health Services Research, University of Maryland School of Pharmacy, Baltimore, MD, USA; Peter Lamy Center on Drug Therapy and Aging, University of Maryland School of Pharmacy, Baltimore, MD, USA. Electronic address: bstuart@rx.umaryland.edu.
authors.forename: Bruce
authors.initials: B
authors.lastname: Stuart
authors.affiliation: Department of Pharmaceutical Health Services Research, University of Maryland School of Pharmacy, Baltimore, MD, USA. Electronic address: rbeardsl@rx.umaryland.edu.
authors.forename: Robert
authors.initials: R
authors.lastname: Beardsley
authors.affiliation: Department of Epidemiology and Public Health, University of Maryland School of Medicine, Baltimore, MD, USA. Electronic address: cbrown@epi.umaryland.edu.
authors.forename: Clayton
authors.initials: C
authors.lastname: Brown
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000978:Antiparkinson Agents / Q000627:therapeutic use*; D015331:Cohort Studies; D005260:Female; D005102:Health Expenditures; D006801:Humans; D008297:Male; D055118:Medication Adherence; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D010300:Parkinson Disease / Q000188:drug therapy* / Q000191:economics / Q000523:psychology; D010342:Patient Acceptance of Health Care / Q000706:statistics & numerical data*
chemical_list: D000978:Antiparkinson Agents
keywords: Antiparkinson regimen modifications; Medicare; Medication nonadherence