Cost sharing, adherence, and health outcomes in patients with diabetes.
OBJECTIVE
To assess the relationship between cost sharing and adherence to antidiabetic medications in patients with type 2 diabetes and to examine the relationship between medication adherence and outcomes, including complication rates, medical service utilization, and workplace productivity measures.


METHODS
A retrospective, cross-sectional study analyzing the healthcare experience of patients with type 2 diabetes on oral antidiabetic medication (OAD) with or without insulin (n = 96,734) and patients on OAD only (n = 55,356) with employer-sponsored insurance in the 2003-2006 MarketScan Database.


METHODS
Using a 2-stage residual inclusion model, the first stage estimated the effects of cost sharing on adherence to antidiabetic medications in an 18-month time frame (January 2003 through June 2004). Adherence was determined from the percentage of days covered. The second stage estimated the effects of adherence on complication rates (eg, retinopathy, neuropathy, peripheral vascular disease), medical service utilization rates, and measures of productivity (absence days and short-term disability days) in the subsequent 2 years (July 2004 through June 2006).


RESULTS
A $10 increase in the patient cost-sharing index resulted in a 5.4% reduction in adherence to antidiabetic medications for patients on OAD only and a 6.2% reduction in adherence for patients on OAD with or without insulin. Adherence was associated with lower rates of complications (eg, amputation/ulcers, retinopathy) and also was associated with fewer emergency department visits and short-term disability days.


CONCLUSIONS
Medical plans, employers, and policy makers should consider implementing interventions targeted to improve antidiabetic medication adherence, which may translate to better outcomes.
Gibson
Teresa B
TB
Thomson Reuters Healthcare, Ann Arbor, MI 48108, USA. teresa.gibson@thomsonreuters.com
Song
Xue
X
Alemayehu
Berhanu
B
Wang
Sara S
SS
Waddell
Jessica L
JL
Bouchard
Jonathan R
JR
Forma
Felicia
F
D016001:Confidence Intervals; D017047:Cost Sharing / Q000191:economics* / Q000706:statistics & numerical data; D003430:Cross-Sectional Studies; D016208:Databases, Factual; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy / Q000191:economics*; D004526:Efficiency; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D007004:Hypoglycemic Agents / Q000191:economics* / Q000627:therapeutic use; D007297:Inpatients / Q000706:statistics & numerical data; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D018803:Models, Economic; D015999:Multivariate Analysis; D016017:Odds Ratio; D012189:Retrospective Studies; D012307:Risk Factors; D016896:Treatment Outcome; D014481:United States; D017132:Workplace; D016903:Drug Monitoring
D007004:Hypoglycemic Agents