This paper was presented at the 29th International Conference on Pharmacoepidemiology and Therapeutic Risk Management, Montreal, August 25–28, 2013. It received ‘Best Poster Award’ from the Comparativeness Effectiveness Special Interest Group.
Instrumental variable applications using nursing home prescribing preferences in comparative effectiveness research†
Article first published online: 24 MAR 2014
Copyright © 2014 John Wiley & Sons, Ltd.
Pharmacoepidemiology and Drug Safety
Volume 23, Issue 8, pages 830–838, August 2014
How to Cite
2014), Instrumental variable applications using nursing home prescribing preferences in comparative effectiveness research, Pharmacoepidemiol Drug Saf, 23: 830–838. DOI: 10.1002/pds.3611, , , , , and , (
- Issue published online: 28 JUL 2014
- Article first published online: 24 MAR 2014
- Manuscript Accepted: 17 FEB 2014
- Manuscript Revised: 2 FEB 2014
- Manuscript Received: 10 OCT 2013
- Agency for Healthcare Research and Quality.. Grant Number: HHSA 290-2005-00161
- National Institute of Mental Health. Grant Number: K01 MH099141
- epidemiologic methods;
- instrumental variable;
- comparative effectiveness;
- nursing home;
- prescribing preference;
Nursing home residents are of particular interest for comparative effectiveness research given their susceptibility to adverse treatment effects and systematic exclusion from trials. However, the risk of residual confounding because of unmeasured markers of declining health using conventional analytic methods is high. We evaluated the validity of instrumental variable (IV) methods based on nursing home prescribing preference to mitigate such confounding, using psychotropic medications to manage behavioral problems in dementia as a case study.
A cohort using linked data from Medicaid, Medicare, Minimum Data Set, and Online Survey, Certification and Reporting for 2001–2004 was established. Dual-eligible patients ≥65 years who initiated psychotropic medication use after admission were selected. Nursing home prescribing preference was characterized using mixed-effects logistic regression models. The plausibility of IV assumptions was explored, and the association between psychotropic medication class and 180-day mortality was estimated.
High-prescribing and low-prescribing nursing homes differed by a factor of 2. Each preference-based IV measure described a substantial proportion of variation in psychotropic medication choice (β(IV treatment): 0.22-0.36). Measured patient characteristics were well balanced across patient groups based on instrument status (52% average reduction in Mahalanobis distance). There was no evidence that instrument status was associated with markers of nursing home quality of care.
Findings indicate that IV analyses using nursing home prescribing preference may be a useful approach in comparative effectiveness studies, and should extend naturally to analyses including untreated comparison groups, which are of great scientific interest but subject to even stronger confounding. Copyright © 2014 John Wiley & Sons, Ltd.