Clinical trials have been used for years and touted as the most reliable testing method for drugs, medical devices and procedures. However, new research indicates that elderly people are often left out of clinical trials.

More than half of clinical trials exclude people based on their age or age-related conditions, according to a new study by Robert Wood Johnson Foundation Clinical Scholars at the University of Michigan.

Twenty percent of clinical trials exclude people based on their age alone, and 45 percent of the trials that didn't have age limits excluded people for having other illnesses, cognitive impairment, a reduced life expectancy, physical disabilities, functional limitations, or living in a nursing home – all restrictions that tend to remove the elderly from the mix. Furthermore, only one in four trails examined outcomes that are highly relevant to older adults.

As a result, the people enrolled in the trial are quite different from those who will actually use the drug or undergo the procedure in the real world.

What does this mean for elderly people and their caregivers? Lead researcher Dr. Donna Zulman, who is also an instructor at Stanford University, told AgingCare.com that excluding the elderly population can make the data less reliable and undermine treatment. "There is the potential for adverse consequences," she explained. "The risks and benefits are very different for older patients. Trials that exclude older individuals may fail to catch that a certain treatment has increased risks of side effects in elderly people. That might make the research findings irrelevant for treating vulnerable older patients."

Dr. Zulman says including older people with complex health problems in clinical trials can be technically challenging and increase the cost of the trials.

Authors of the study call on the FDA, National Institutes of Health and sponsors of clinical trials to put policies in place to require the older demographic to be represented in clinical trials – particularly when they are studying conditions that are common among elderly people.