Effect of increased cost-sharing on oral hypoglycemic use in five managed care organizations: how much is too much?
BACKGROUND
For patients with a chronic disease, increased cost-sharing for medications may lead to unintended consequences, including reduced use of medications essential for control of their disease.


OBJECTIVE
The objective of this study was to estimate the effects of small ($1-6 per 30-day supply), moderate ($7-10), and large (>$10) increases in medication cost-sharing on 12-month trends in oral hypoglycemic (OH) use among adults with type 2 diabetes.


METHODS
We conducted a quasiexperimental study using a time series with comparison group design. Data were obtained from computerized membership, benefit, and pharmacy dispensing data of 5 managed care organizations (MCOs). A total of 13,110 12-month episodes of OH use and a medication cost-sharing increase ("intervention") were matched with 13,110 that had no increase. The dependent variable was OH average daily dose (ADD) standardized to each episode's mean OH ADD in the 6-month preintervention period. The principal independent variable was change in cost per 30-day OH supply between the 6-month pre- and postintervention periods. Effects of changes in cost-sharing on OH ADD were estimated using segmented time series regression.


RESULTS
Episodes with >$10 increase in cost-sharing had significantly (alpha=0.05) decreased OH ADD in the postintervention period. At 6 months after this increase, OH ADD had decreased by 18.5% from that predicted from the preintervention trend. Episodes with a $1 to $10 increase in cost-sharing and those with no increase in cost-sharing had significant linear increases in OH use over the 12-month period.


CONCLUSIONS
Large increases in medication cost-sharing were associated with immediate and persistent reductions in OH use. Small and moderate increases had little effect on OH use in the 6-month period after the increase.
Roblin
Douglas W
DW
Research Department, Kaiser Permanente, Atlanta, Georgia 30305, and the Department of Ambulatory Care and Prevention, Harvard Medical School and Harvard Pilgrim Health Care, Boston, Massachusetts, USA. Douglas.Roblin@KP.ORG
Platt
Richard
R
Goodman
Michael J
MJ
Hsu
John
J
Nelson
Winnie W
WW
Smith
David H
DH
Andrade
Susan E
SE
Soumerai
Stephen B
SB
D000293:Adolescent; D000328:Adult; D000368:Aged; D002908:Chronic Disease / Q000188:drug therapy / Q000191:economics; D017047:Cost Sharing; D016208:Databases, Factual; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy* / Q000191:economics*; D017050:Episode of Care; D005382:Financing, Personal; D006801:Humans; D007004:Hypoglycemic Agents / Q000008:administration & dosage / Q000191:economics* / Q000627:therapeutic use; D008329:Managed Care Programs / Q000191:economics; D008875:Middle Aged; D010349:Patient Compliance / Q000706:statistics & numerical data*; D011306:Prescription Fees; D012044:Regression Analysis; D012646:Self Administration / Q000706:statistics & numerical data*; D014481:United States
D007004:Hypoglycemic Agents