The vast majority of older adults in the United States regularly use medications. A recent survey found that of US adults aged 65 and older who were not hospitalized or living in nursing homes, more than 90% used at least one medication per week, more than 40% used five or more different medications per week, and 12% used ten or more different medications per week.

Despite this widespread use of medications, little evidence exists detailing the incidence and preventability of adverse drugs events in geriatric outpatients. A group of Massachusetts-based researchers recently set out to fill this knowledge gap.

In a study published in the March 5, 2003 Journal of the American Medical Association (JAMA), the researchers reported that adverse drug events among geriatric outpatients are common, and that more than one-quarter of these events may be preventable.

About the Study

The researchers analyzed the nature and incidence of drug-related events among 27,617 Medicare enrollees, aged 65 years and older, who were cared for by a multispecialty group practice in a health maintenance organization between July 1, 1999 and June 30, 2000. This information was culled from reports from healthcare professionals, hospital discharge summaries, emergency department notes, electronic clinic notes, and administrative incidence reports.

An adverse event was defined as an injury resulting from the use of a drug.

The Findings

The researchers identified 1523 adverse drug events, of which 27.6% were considered preventable. The overall rate of adverse drug events was 50.1 per 1000 person-years, with a rate of 13.8 preventable adverse drug events per 1000 persons per year.

The researchers categorized adverse events as follows:

  • Significant: ex. falls without associated fracture; hemorrhage not requiring transfusion or hospitalization
  • Serious: ex. falls with an associated fracture; hemorrhage requiring transfusion or hospitalization
  • Life-threatening: ex. renal failure requiring hospitalization; brain injury due to protracted low blood sugar
  • Fatal

Of the adverse events, 578 (38.0%) were considered serious, life threatening, or fatal. Of these, 42.2% were deemed preventable, compared to 18.7% of the significant adverse effects. More severe adverse effects were significantly more likely to be considered preventable.

Preventable adverse effects were most often due to errors in monitoring (60.8%) and prescribing (58.4%), including inadequate laboratory monitoring of drug therapies or prescription of the wrong drug. Errors of patient adherence, such as taking the wrong dose or refusing to take a needed medication, accounted for 21.1% of preventable adverse effects.

The medication classes most frequently associated with adverse drug events were cardiovascular drugs (26.0%), antibiotics/anti-infectives (14.7%), and diuretics (13.3%). Drug classes associated with more adverse effects were also among those most frequently prescribed for geriatric outpatients.

How Does This Affect You?

Although the results of this study show a disturbing frequency of adverse drug events in elderly outpatient populations, they do suggest that a large percentage of those events are preventable. The study also highlights several areas to target for prevention of such events.

For example, one way to potentially reduce the rate of adverse effects is through computerized prescription systems that automatically warn patients and providers of harmful drug interactions. The researchers propose better collaboration between those who prescribe drugs and the clinical pharmacists, who know the most about them.

Another opportunity to reduce the risk of adverse drug events lies in changing patient behavior. This study found that more than 20% of adverse events are due to errors of patient adherence. However, current methods of patient education—based largely on poorly coordinated interactions between physicians, pharmacists, and patients—do not appear to be working adequately. New strategies that enable older patients and their caregivers to take better control of drug therapies could be safer and more effective for older adults.