Only 29% of seniors who take five or more prescription drugs have had a comprehensive medication review to avert potential interactions, according to new findings from the University of Michigan’s National Poll on Healthy Aging.

Not surprisingly, the poll also found that the number of prescriptions rose along with age. Fully 30% of those aged 65 and older took five or more medications, compared with 19% of those aged 50 to 64. And respondents over age 65 also said they take five or more over-the-counter medications, vitamins and supplements, compared with 9% of those in their 50s and early 60s.

Poll responses also appeared to explain low participation in the free Medicare Part D review benefit. Most beneficiaries who had not had a medication review were unaware that they may be eligible under this or other health plans.

Investigators did find a bright spot: More than a third of older adults said that they would be interested in checking their medication list with a pharmacist.

Ideally, every older person should keep a list of everything they take, whether prescribed or purchased directly, said poll director Preeti Malani, M.D. Providers or pharmacists can use this to identify potential interactions, she said.

The new report, published Wednesday, drew from a national sample of more than 2,000 adults aged 50 to 80.