title: Impact of type 2 diabetes medication cost sharing on patient outcomes and health plan costs.
abstract: To study the association between cost sharing for diabetes medications, adherence, hospitalization rates, and healthcare costs, with relationship to patient risk.
  
  
  
  A retrospective claims analysis of data from 35 large, private, self-insured employers (2004 to 2012).
  
  
  
  We examined outcomes for 92,410 patients aged 18 to 64 years with a type 2 diabetes (T2D) diagnosis who filled at least 1 T2D prescription. First, we examined the relationship between adherence, measured as the proportion of days covered, and cost sharing, measured as the out-of-pocket cost to purchase a pre-specified bundle of T2D prescriptions. We then examined the association between adherence and hospital days. Simulations showed the effect of increased cost sharing on adherence and inpatient utilization.
  
  
  
  A $10 increase in out-of-pocket cost was associated with a 1.9% reduction in adherence (P < .01). In turn, a 10% reduction in adherence was associated with a 15% increase in per-patient hospital days (0.17 days; P < .01). For the average plan, switching from low to high cost sharing reduced per-patient medication costs by $242 and increased per-patient hospitalization costs by $342, for a net increase of $100 in plan costs. Increases in per-patient costs were greater for high-risk patients, such as those with heart failure ($1328).
  
  
  
  Increased cost sharing for T2D medication was associated with reductions in pharmacy costs, but higher total costs for patients with T2D. This problem is particularly acute for patients with 1 or more cardiovascular comorbidities. The results suggest that increased diabetes cost sharing may hamper efforts to lower the total cost of diabetes care.
authors.forename: Julia
authors.initials: J
authors.lastname: Thornton Snider
authors.forename: Seth
authors.initials: S
authors.lastname: Seabury
authors.forename: Janice
authors.initials: J
authors.lastname: Lopez
authors.forename: Scott
authors.initials: S
authors.lastname: McKenzie
authors.affiliation: Schaeffer Center for Health Policy and Economics, University of Southern California, 635 Downey Way, VPD Ste 210, Los Angeles, CA 90089-3333. E-mail: dana.goldman@usc.edu.
authors.forename: Dana P
authors.initials: DP
authors.lastname: Goldman
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D017047:Cost Sharing / Q000639:trends*; D016208:Databases, Factual; D003924:Diabetes Mellitus, Type 2 / Q000175:diagnosis / Q000188:drug therapy* / Q000191:economics; D016527:Drug Costs; D005260:Female; D017048:Health Care Costs; D006760:Hospitalization / Q000191:economics / Q000706:statistics & numerical data; D006801:Humans; D007345:Insurance Claim Review; D007348:Insurance, Health / Q000191:economics*; D007356:Insurance, Pharmaceutical Services / Q000191:economics*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014481:United States