Talk to the Veterans Crisis Line now
U.S. flag
An official website of the United States government

VA Health Systems Research

Go to the VA ORD website
Go to the QUERI website
Publication Briefs

Common Cause of Unplanned Hospitalizations among Older Veterans: Adverse Drug Reactions Associated with Polypharmacy

Adverse drug reactions (ADRs) are a significant public health concern as they are a major cause of morbidity and mortality, particularly among older adults. One of the worst consequences of ADRs in older adults is hospitalization and its related costs. Polypharmacy (multiple medication use) is common in community-dwelling older adults and has been shown to be the most consistent and strongest predictor of ADRs in older adults. This retrospective cohort study sought to describe the prevalence of unplanned hospitalizations caused by ADRs (determined using a reliable and valid algorithm) among older Veterans (age > 65 years) between 10/03 and 9/06. In addition, the preventability of unplanned hospitalizations was evaluated. Using VA data, investigators identified 678 randomly selected, unplanned hospitalizations across all 152 VAMCs. For this study, polypharmacy was defined as the use of five or more regularly scheduled medications prescribed by a VA physician just prior to the time of hospitalization. Control variables that were assessed included patient demographics, health status (e.g., comorbidities, psychiatric conditions), and access to care.


  • Adverse drug reactions are a common cause of unplanned hospitalization among older Veterans, are frequently preventable, and are associated with polypharmacy (overall, 45% of Veterans took >9 outpatient medications and 35% took 5 to 8). The most common ADRs that occurred were bradycardia, hypoglycemia, falls, and mental status changes.
  • Of the 678 unplanned hospitalizations that occurred during the study period, 70 ADRs involving 113 drugs occurred in 68 (10%) older Veterans, of which 37% (25/68) were preventable. Extrapolating to a population of more than 2.4 million older Veterans receiving care during this time, 8,000 hospitalizations costing about $110 million (using FY04 dollars) may have been unnecessary.
  • The most common reason for a preventable ADR was suboptimal prescribing (52%), followed by patient non-adherence (28%), and suboptimal monitoring (12%). In addition, 4 medication classes (cardiovascular, central nervous system, anti-thrombotic, and endocrine) accounted for almost 80% of all the drugs implicated in ADRs.


  • This study was limited to older Veterans and relied heavily on data from electronic health records to assess ADRs. Results may have been underestimated if information was missing or entered incorrectly.
  • It is possible that unmeasured confounding could account for the association between polypharmacy and ADRs.


  • This information highlights possible areas of intervention (e.g., reducing unnecessary polypharmacy) to decrease preventable ADR-related hospitalizations.
  • Investigators are working with their local GRECC to disseminate through Geriatric Care at the VHA National level and to develop an intervention to improve care for older Veterans.

This study was partly funded by HSR&D (IIR 06-062). Drs. Marcum and Hanlon are part of HSR&D’s Center for Health Equity Research and Promotion, Pittsburgh, PA.

PubMed Logo Marcum Z, Amuan M, Hanlon J, et al. Prevalence of Unplanned Hospitalizations Caused by Adverse Drug Reactions among Older Veterans. Journal of the American Geriatrics Society December 8, 2011;e-pub ahead of print.

Related Briefs

» next 44 Elder Care Briefs...

» next 171 Medication Briefs...

What are HSR Publication Briefs?

HSR requires notification by HSR-funded investigators about all articles accepted for publication. These journal articles are reviewed by HSR and publication briefs or summaries are written for a select number of articles that are then forwarded to VHA Central Office leadership to keep them informed about important findings or information. Articles to be summarized are selected by HSR based on timeliness of the findings, interest of leadership, or potential impact on the organization. Publication briefs are written for only a small number of HSR published articles. Visit the HSR citations database for a complete listing of HSR articles and presentations.

Questions about the HSR website? Email the Web Team

Any health information on this website is strictly for informational purposes and is not intended as medical advice. It should not be used to diagnose or treat any condition.