title: An analysis of disenrollment from Medicare managed care plans by Medicare beneficiaries with diabetes.
abstract: OBJECTIVE
  The purpose of this work is to determine whether high-cost high-risk Medicare patients with diabetes in managed care plans disenroll more quickly than lower-cost lower-risk Medicare patients with diabetes. If high-cost high-risk patients with diabetes do disenroll more quickly, Medicare managed care plans benefit financially from favorable disenrollment.
  
  
  METHODS
  Time in a health maintenance organization (HMO) was modeled using a duration model with the number of months in the HMO as the dependent variable, controlling for censoring. Data were drawn from a representative sample of Medicare patients with diabetes in the FFS sector in 1994. The panel was followed for 4 years, 1995-1998. The sample included all 6839 individuals who enrolled in a Medicare HMO for at least 1 month during the 48-month observation window.
  
  
  RESULTS
  We found a statistically significant negative association between the time in an HMO and pre-enrollment Part B expenditures (beta = -0.00001, t = -4.39) and any Part A expenditures (beta = -0.465, t = -1.98), and 2 of 4 diabetic complications (heart complications: beta = -0.0773, t = -4.61; vision complications beta = -0.2474, t = -1.94). Of the plan characteristics, only the drug benefit variable (beta = 0.151, t = 5.64) had a statistically significant coefficient.
  
  
  CONCLUSIONS
  Overall, our results support the hypothesis that high-cost, high-risk individuals disenroll from Medicare HMOs sooner than lower-cost lower-risk individuals. However, this effect is mitigated by plans offering better prescription drug benefits. We did find some evidence that patients with diabetes with very high pre-enrollment Part A costs may remain longer in HMOs relative to patients with diabetes with lower Part A prior year expenditures.
authors.affiliation: Department of Health Policy and Management, Rollins School of Public Health, Emory University, Atlanta, Georgia 30322, USA. aatherl@sph.emory.edu
authors.forename: Adam
authors.initials: A
authors.lastname: Atherly
authors.forename: Paul L
authors.initials: PL
authors.lastname: Hebert
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Maciejewski
mesh_terms: D000368:Aged; D002755:Choice Behavior; D048909:Diabetes Complications / Q000191:economics; D003920:Diabetes Mellitus / Q000145:classification / Q000191:economics*; D011307:Drug Prescriptions / Q000191:economics; D005102:Health Expenditures / Q000706:statistics & numerical data*; D006279:Health Maintenance Organizations / Q000191:economics / Q000706:statistics & numerical data*; D006801:Humans; D016344:Medicare Part A / Q000191:economics*; D016345:Medicare Part B / Q000191:economics*; D017059:Models, Econometric; D017060:Patient Satisfaction; D012306:Risk; D013997:Time Factors; D014481:United States