Older Americans are taking more medications, with 1 in 5 at risk for a major drug interaction

Older Americans are increasingly taking multiple prescription medications and dietary supplements. Although the prevalence of potentially major drug-drug interactions has declined slightly, more than 1 in 5 older adults are potentially at risk, according to a USC-led study published September 24 in JAMA.

The research was led by Dima Mazen Qato of the USC Mann School of Pharmacy and Pharmaceutical Sciences and the USC Schaeffer Center for Health Policy & Economics, in collaboration with researchers from the Johns Hopkins Bloomberg School of Public Health and NORC at the University of Chicago.

Using nationally representative data from nearly 5,000 community-dwelling U.S. adults ages 62 to 85, researchers compared medication and supplement use in 2015–2016 with use in 2021–2023.

They found that polypharmacy, defined as taking five or more prescription medications at the same time, increased from 31% to 35.7%. Dietary supplement polypharmacy also increased, from 12.6% to 16.7%.

The concurrent use of drug regimens with potentially major interactions declined from 25.7% to 22.3%. However, the therapeutic classes most frequently involved in these regimens remained largely unchanged. In 2021-23, more than 1 in 5 older adults were taking medications that placed them at risk for a potentially major drug interaction.

Antidepressants, statins and antiplatelet therapies were the most commonly used medications involved in potentially major interactions among older adults.

“These findings underscore the need for continuing efforts to improve medication safety among older adults,” Qato said. “Efforts to reduce polypharmacy and harmful drug interactions should focus on commonly used interacting regimens, particularly those involving antidepressants.”

The study’s co-authors are Shyam Krishnan Ondanat Veetil and Qingrong “Jessica” Li of USC Mann; Jocelyn Wilder of NORC at the University of Chicago; and Rupshikha Sen and G. Caleb Alexander of the Johns Hopkins Bloomberg School of Public Health.

The study used data from the National Social Life, Health and Aging Project, which is supported by the National Institute on Aging (R01AG043538).