>>See the complete list of medications studied.
Researchers at Indiana University School of Medicine studied the physical changes in the brain when patients use these types of drugs.
The researchers found that the medications lower metabolism and reduced the size of study participants' brains.
The study examined 451 people with an average age of 72. Sixty of them were taking at least one medication with medium or high anticholinergic activity, CNN reported.
>>Read the study's findings here.
Researchers used cognitive tests, PET scans and MRI scans to see brain activity and structure.
The tests showed that people taking the medications performed worse on short-term memory tests and other tests including ones that examined verbal reasoning, planning and problem solving.
An earlier study found that the medications could impair brain function when taking them for as few as 60 continuous days.