Older people who take certain medicines to treat conditions like urinary incontinence, depression, asthma, allergies, and sleeping problems should be warned that their use may bring a higher risk of dementia, scientists say.
A small Indiana University study found that people using "anticholinergic medications" did worse on thinking-related tests and had smaller brain sizes than those who didn't take them.
The researchers say that although a link has been found before, this might be the first time that their effect at blocking a brain chemical called acetylcholine has been implicated.
But the study showed an association, and it can't prove these drugs cause dementia.
See a list of drugs the researchers studied.
"These findings provide us with a much better understanding of how
this class of drugs may act upon the brain in ways that might raise the risk of cognitive impairment and dementia," says Shannon Risacher, PhD, assistant professor of radiology and imaging sciences, in a statement.
The latest research project, published in JAMA Neurology, involved 451 people with an average age of 73.3 years, 60 of who were taking at least one medication from this class of drugs.
Tests on their brain function revealed that those taking the anticholinergic medications did worse than those not taking the drugs. These included results on short-term memory, verbal reasoning, planning, and problem solving.
The researchers also found that anticholinergic medications led to users' brains processing blood sugar (glucose) -- a sign of brain activity -- differently in both the overall brain and in the hippocampus, a region that's tied to memory and which shows early effects of Alzheimer's disease.
Smaller Brain Volume
Another discovery was that volunteers using anticholinergic drugs had less brain volume and larger ventricles, the cavities inside the brain.
"Given all the research evidence, physicians might want to consider alternatives to anticholinergic medications if available when working with their older patients," Risacher says.
Commenting on the study in an emailed statement, Dr. Rosa Sancho, head of research at Alzheimer’s Research UK, says: "This small study adds to evidence for an association between anticholinergic medicines, memory difficulties, and changes in brain biology, but from this research we can’t conclude that this particular type of drug causes dementia.
"There are many different lifestyle factors that could explain the apparent link between this particular class of medicine and the changes seen in this study, and larger and longer studies are necessary to understand the true long-term impact of these drugs on the brain.
"Anticholinergics can have many beneficial effects, and these need to be balanced against potential side effects, but anybody concerned about their current medication should speak to a doctor before stopping a course of treatment."