Volume 49 | Number 4 | August 2014

Abstract List

Bruce Stuart Ph.D., F. Ellen Loh M.B.A., B.S.Pharm., Pamela Roberto M.P.P., Laura Miller Ph.D.


To develop and test incident drug user designs for assessing cost savings from statin use in diabetics.

Data Source

Random 5 percent sample of Medicare beneficiaries, 2006–2008.

Study Design

Seven‐step incident user design to assess impact of statin initiation on subsequent Medicare spending: (1) unadjusted pre/post initiation test; (2) unadjusted difference‐in‐difference () with comparison series; (3) adjusted ; (4) propensity score ()‐matched with static and dynamic baseline covariates; (5) ‐matched by drug adherence strata; (6) ‐matched for high adherers controlling for healthy adherer bias; and (7) replication for ‐inhibitor/ initiators.

Data Collection/Extraction Methods

Subjects with prevalent diabetes and no statin use (January–June 2006) and statin initiation (July 2006–January 2008) compared to nonusers with a random “potential‐initiation” month. Monthly Medicare spending tracked 24 months pre‐ and post‐initiation.

Principal Findings

Statistically significant savings in Medicare spending were observed beginning 7 months post‐initiation for statins and 13 months post‐initiation for s/s. However, these savings were only observed for adherent patients in steps 5 and 6.


Drug initiator designs are more robust to confounding than prevalent user designs in assessing cost‐offsets from drug use but still require other adjustments and sensitivity analysis to ensure proper inference.