title: Antiparkinson drug adherence and its association with health care utilization and economic outcomes in a Medicare Part D population.
abstract: OBJECTIVE
  We examine the associations of adherence to antiparkinson drugs (APDs) with health care utilization and economic outcomes among patients with Parkinson's disease (PD).
  
  
  METHODS
  By using 2006-2007 Medicare administrative data, we examined 7583 beneficiaries with PD who filled two or more APD prescriptions during 19 months (June 1, 2006, to December 31, 2007) in the Part D program. Two adherence measures--duration of therapy (DOT) and medication possession ratio (MPR)--were assessed. Negative binomial and gamma generalized linear models were used to estimate the rate ratios (RRs) of all-cause health care utilization and expenditures, respectively, conditional upon adherence, adjusting for survival risk, sample selection, and health-seeking behavior.
  
  
  RESULTS
  Approximately one-fourth of patients with PD had low adherence (MPR < 0.80, 28.7%) or had a short DOT (≤ 400 days, 23.9%). Increasing adherence to APD therapy was associated with decreased health care utilization and expenditures. For example, compared with patients with low adherence, those with high adherence (MPR = 0.90-1.00) had significantly lower rates of hospitalization (RR = 0.86), emergency room visits (RR = 0.91), skilled nursing facility episodes (RR = 0.67), home health agency episodes (RR = 0.83), physician visits (RR = 0.93), as well as lower total health care expenditures (-$2242), measured over 19 months. Similarly, lower total expenditure (-$6308) was observed in patients with a long DOT versus those with a short DOT.
  
  
  CONCLUSIONS
  In this nationally representative sample, higher adherence to APDs and longer duration of use of APDs were associated with lower all-cause health care utilization and total health care expenditures. Our findings suggest the need for improving medication-taking behaviors among patients with PD to reduce the use of and expenditures for medical resources.
authors.affiliation: Department of Pharmaceutical Health Services Research, University of Maryland School of Pharmacy, Baltimore, MD, USA. Electronic address: ywei@rx.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.
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.
authors.forename: Linda
authors.initials: L
authors.lastname: Simoni-Wastila
authors.affiliation: Department of Neurology, University of Maryland School of Medicine, Baltimore, MD, USA.
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.
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.
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.
authors.forename: Clayton H
authors.initials: CH
authors.lastname: Brown
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000978:Antiparkinson Agents / Q000008:administration & dosage / Q000191:economics / Q000627:therapeutic use*; D003430:Cross-Sectional Studies; D005260:Female; D005102:Health Expenditures / Q000706:statistics & numerical data; D006296:Health Services / Q000191:economics / Q000706:statistics & numerical data*; D006801:Humans; D016014:Linear Models; D008297:Male; D054524:Medicare Part D / Q000191:economics*; D055118:Medication Adherence; D008875:Middle Aged; D010300:Parkinson Disease / Q000188:drug therapy* / Q000191:economics; D010342:Patient Acceptance of Health Care / Q000706:statistics & numerical data; D012189:Retrospective Studies; D013997:Time Factors; D014481:United States
chemical_list: D000978:Antiparkinson Agents
keywords: Medicare; antiparkinson drug; expenditures; health care utilization; medication adherence