People over the age of 65 make up 15 percent of the U.S. population but consume more than one third of the prescription drugs. A new study from researchers at Duke University examines the prescription patterns of the elderly to see if some of their pills may be endangering seniors' health.

What the researchers wanted to know: Are senior citizens being prescribed drugs that have been shown to be dangerous for the elderly?

What they did: The researchers examined data from 765,423 people older than 65 who filed claims in 1999 through a large company that manages prescriptions from all over the country. They compared prescriptions filled to a list of 28 drugs and classes of drugs that could be dangerous for seniors, known as the Beers list. Mark Beers developed the list in 1991 with a panel of experts to determine which drugs should be used in nursing homes, though the list was updated and expanded in 1997 to include all settings. .

What they found: Twenty-one percent of the subjects in the study, 162,370 people, filled prescriptions for drugs on the Beers list. Forty-one percent of the inappropriate prescriptions were for drugs to treat mental illnesses, such as depression, and nearly 1 in 20 people received prescriptions for more than one drug from the Beers list. These results are similar to earlier studies done with different data.

What it means to you: Seniors who are concerned, or who are receiving multiple drugs, should check with their doctor about the Beers list and how it might affect them. There are a number of reasons why these drugs might be being prescribed to individual patients that are legitimate, so just because you are receiving a drug from that list does not necessarily mean you need to stop taking it. (See caveats below.)

Caveats: To start with, the study looked at a very simple set of data, which showed only which drugs were prescribed, not why they were prescribed. So, it's very possible that, even knowing a drug was on the Beers list, a doctor would still decide it was the best fit for an individual patient's condition. Second, the Beers list is based on expert opinions and has not been tested by a scientific study, so it is quite imperfect. Further, seniors are often excluded from clinical trials so the side effects of some drugs on seniors' health is not well-known. The authors call for more clinical trials involving seniors to remedy that last problem.

Find out more: The Beers List is available in PDF format, meaning you will need the Adobe Acrobat program to read it, at the Texas Association of Homes and Services for the Aging website.

The National Council on Patient Information and Education has a nice Web page with information on what to do once you have a new prescription, including what questions to ask your doctor and pharmacist.

Read the article: Curtis, L.H., Ostby, T., Sendersky, V., Hutchison, S., Dans, P.E., Wright, A., Woosley, R.L., Schulman, K.A. "Inappropriate Prescribing for Elderly Americans in a Large Outpatient Population." Archives of Internal Medicine. Aug. 9, 2004. Vol. 164, No. 15, pp. 1621–1625.

Abstract online: http://archinte.ama-assn.org