CHICAGO, Dec. 24 (Xinhua) -- One in 25 older adults risk dangerous drug interactions in the United States, according to a new study available here on Wednesday.

    The study by researchers at the University of Chicago Medical Center says at least 2.2 million adults take medicine in combinations that could trigger dangerous interactions causing gastrointestinal bleeding, muscle breakdown, disruption in heart rhythm and other serious problems. Half of the interactions involved over-the-counter medications, such as aspirin or dietary supplements.

    According to the study published in the latest issue of the Journal of American Medical Association, risks might be even higher because the research focused only on major interactions among the 20 most common drugs and dietary.

    The most common problematic combination of non-prescription drugs was ginkgo biloba and aspirin. Taking the two together can increase the risk of internal bleeding, the study says.

    Older people are taking more drugs than ever as a result of more intense treatments for chronic illness, improved access to medications and the growth of the generic drug market. More than half of older adults now take five or more medications or supplements. Older people also are more likely to suffer from multiple illnesses, according to the study.