title: Adherence to statin therapy under drug cost sharing in patients with and without acute myocardial infarction: a population-based natural experiment.
abstract: BACKGROUND
  As medication spending grows, Medicare Part D will need to adapt its coverage policies according to emerging evidence from a variety of insurance policies. We sought to evaluate the consequences of copayment and coinsurance policies on the initiation of statin therapy after acute myocardial infarction and adherence to therapy in statin initiators using a natural experiment of all British Columbia residents aged 66 years and older.
  
  
  RESULTS
  Three consecutive cohorts that included all patients who began statin therapy during full drug coverage (2001), coverage with a $10 or $25 copay (2002), and coverage with a 25% coinsurance benefit (2003-2004) were followed up with linked healthcare utilization data (n=51,561). Follow-up of cohorts was 9 months after each policy change. Adherence to statin therapy was defined as > or = 80% of days covered. Relative to full-coverage policies, adherence to new statin therapy was significantly reduced, from 55.8% to 50.5%, under a fixed copayment policy (-5.4% points; 95% CI, -6.4% to -4.4%) and the subsequent coinsurance policy (-5.4% points; 95% CI, -6.3% to -4.4%). An uninterrupted increase in the proportion of patients initiating statin therapy after an acute myocardial infarction (1.7% points per quarter) was observed over the study period, similar to a Pennsylvania control population with full coverage. Sudden changes to full out-of-pocket spending, similar to Medicare's Part D "doughnut hole," almost doubled the risk of stopping statins (adjusted odds ratio, 1.94, 95% CI, 1.82 to 2.08).
  
  
  CONCLUSIONS
  Fixed patient copayment and coinsurance policies have negative effects on adherence to statin lipid-lowering drug therapy but not on their initiation after myocardial infarction.
authors.affiliation: Division of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, 1620 Tremont St, Suite 3030, Boston, MA 02120, USA. schneeweiss@post.harvard.edu
authors.forename: Sebastian
authors.initials: S
authors.lastname: Schneeweiss
authors.forename: Amanda R
authors.initials: AR
authors.lastname: Patrick
authors.forename: Malcolm
authors.initials: M
authors.lastname: Maclure
authors.forename: Colin R
authors.initials: CR
authors.lastname: Dormuth
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Glynn
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001955:British Columbia; D015331:Cohort Studies; D017047:Cost Sharing / Q000191:economics / Q000706:statistics & numerical data*; D003669:Deductibles and Coinsurance / Q000191:economics / Q000706:statistics & numerical data; D016527:Drug Costs; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000191:economics* / Q000627:therapeutic use; D019458:Insurance Coverage / Q000191:economics / Q000706:statistics & numerical data; D007356:Insurance, Pharmaceutical Services / Q000145:classification / Q000191:economics / Q000706:statistics & numerical data*; D008297:Male; D009203:Myocardial Infarction / Q000188:drug therapy*; D009313:National Health Programs / Q000191:economics / Q000706:statistics & numerical data*; D010349:Patient Compliance / Q000706:statistics & numerical data*
chemical_list: D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors