Seniors are more likely to be admitted to a hospital after outpatient surgery due to misunderstanding discharge and medication instructions, a new study shows.

Researchers looked at data from more than 53,000 Americans who had outpatient surgeries in 2012. Of those patients, those over age 65 were 54% more likely to be readmitted to the hospital within 30 days than those younger than 65. Researchers did not include patients’ health before surgery as a factor in the study.

“Age was the biggest factor associated with readmission and complications,” study author Gildasio De Oliveira Jr., M.D., assistant professor at Northwestern University’s Feinberg School of Medicine told HealthDay. “It’s not because they are sicker, it’s because they are older and have trouble understanding their discharge instructions and medication dosing, which often are not clearly explained.”

Seniors need to be given clearer, more understandable discharge instructions and should be evaluated for their ability to care for themselves after the surgery, De Oliveira recommended.