Preventing dementia has become a top goal for medical experts as cases continue to rise. The most common form of dementia, Alzheimer’s disease, is the sixth-leading cause of death in the United States.

Now a new large study published in the BMJ medical journal provides evidence that a certain type of common drug may increase the risk of developing dementia.

Researchers concluded that people who took class 3 anticholinergic drugs were more likely to develop dementia, even if they took the drugs years before they developed the condition.

Anticholinergic drugs are able to block a neurotransmitter chemical called acetylcholine in the central or peripheral nervous system.

Depending on which part of the nervous system is affected, it can result in a myriad of reactions.

As a result, it’s been used to treat a variety of conditions, including epilepsy, depression, hay fever, urinary incontinence, and Parkinson’s disease symptoms.

What the study revealed

Researchers looked at 40,770 people with dementia and 283,933 people without the disease between 2006 and 2015 to see if the drugs were associated with an increased risk of the condition.

The researchers were based at the University of East Anglia in the United Kingdom, Purdue and Indiana Universities in the United States, and other institutions. It was funded by the U.K.-based Alzheimer’s Society.

The study found that people with dementia were more likely to have taken the stronger class 3 anticholinergic drugs before they developed dementia. The increased risk varied for different types of drugs, but went up to 30 percent in certain cases.

Dr. Gayatri Devi, a neurologist at Lenox Hill Hospital in New York City and author of “The Spectrum of Hope: An Optimistic and New Approach to Alzheimer’s Disease and other Dementias,” explained that the study was a strong one due to its large size and the use of U.K. healthcare databases.  

“Unlike many other studies which rely on patient recall, this study did not, which was a major strength,” Devi told Healthline. “Anticholinergic medications can potentially lower the levels of the brain chemical acetylcholine, which is an important messenger in memory pathways. In this study, use of some (not all) anticholinergic drugs, even as far back as 20 years, previously raised the risk for dementia.”

She pointed out that not all anticholinergic drugs are the same, and some classes didn’t show an increased risk of dementia.

“It was only those drugs with very strong anticholinergic activity that were associated with later dementia,” she said. “Important to note that the drugs did not cause dementia, but the use of the drugs raised the risk for dementia. What this means for us as physicians is to be cautious about the use of such drugs in patients and to use it for as short a time as possible.”

The study’s findings don’t mean patients should always avoid class 3 anticholinergics.

The overall risk to people on these drugs remains relatively low.

For example, a person between 65 and 70 years old has about a 10 percent chance of developing dementia in the next 15 years. If they take anticholinergic antidepressants, they’d have a 19 percent increased risk of dementia. That translates to an additional 1 to 3 more people out of 100 who would receive a dementia diagnosis.

How the research helps doctors, patients

George Savva, PhD, a researcher from University of East Anglia’s School of Health Sciences and one of the co-authors of the study, said the research can provide experts with more evidence to help them make informed decisions about whether or not to prescribe the medication.

“We found that people who had been diagnosed with dementia were up to 30 percent more likely to have been prescribed specific classes of anticholinergic medications,” he said in a statement. “And the association with dementia increases with greater exposure to these types of medication.”

However, Savva and the other researchers made clear they can’t say for certain that this medication causes dementia — just that it’s associated with increased risk.

“It could be that these medications are being prescribed for very early symptoms indicating the onset of dementia,” Savva said. “But because our research shows that the link goes back up to 15 or 20 years before someone is eventually diagnosed with dementia, it suggests that reverse causation, or confounding with early dementia symptoms, probably isn’t the case.”

Dr. Malaz Boustani, MPH, a Regenstrief Institute and Indiana University Center for Aging Research investigator, said in a statement that physicians should think twice about ordering prescriptions for these medications.

Experts already knew that using these drugs could affect cognition and shouldn’t be used in older, frail patients, according to the study authors.

“Physicians should review all the anticholinergic medications — including over-the-counter drugs — that patients of all ages are taking and determine safe ways to take individuals off anticholinergic medications in the interest of preserving brain health,” Boustani said in a statement.

Preserving brain health is key. The Alzheimer’s Association states that the number of Alzheimer’s disease cases alone is expected to nearly triple by 2050.