Long-term use of certain drugs, some of them used to treat depression, has been linked to an increase in dementia risk in a study that looked at 27 million medications and their effects on 40,000 people with dementia compared to 283,000 without the disease.
Researchers at the University of East Anglia in the U.K. found that one type of drug—called anticholinergic drugs, which treat depression, Parkinson’s disease and loss of bladder control—increased a person’s risk of developing dementia by up to 30 percent. Anticholinergic drugs work by blocking acetylcholine, a nervous system neurotransmitter that carries brain signals that control muscles.
The study looked into a link that had been previously established with this particular type of drug, said study authors. They also found that taking the drug even decades before could still heighten risk of dementia. “This study is large enough to evaluate the long-term effect and determine that harm may be experienced years before a diagnosis of dementia is made,” said co-author Noll Campbell, Regenstrief Institute and Indiana University Center for Aging Research investigator.
In the past, researchers found that the risk was still present when the drugs were taken up to 20 years prior to their investigation.
“These findings make it clear that clinicians need to carefully consider the anticholinergic burden of their patients and weigh other options,” said study co-author Malaz Boustani, M.D., a Regenstrief Institute and IU Center for Aging Research investigator and founder of the IU Center for Health Innovation and Implementation Science. “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,” Dr. Boustani said.
This study found that long-term use of some types of anticholinergic drugs increased dementia risk, but not others, like antihistamines and those used for abdominal cramps.
Study authors did not recommend patients stop any medications they are currently taking. And just because a link has been established does not mean that this class of drugs is causing dementia. “The study didn’t investigate what might cause this link between anticholinergics and dementia risk, and researchers will need to build on these findings in future studies,” said Carol Routledge, Alzheimer’s Research U.K. research director.
Overall, those who have taken or are taking anticholinergic drugs should not panic. While a 30 percent increase in risk sounds like a lot, it depends on where a person’s risk started initially based on their genetics and lifestyle factors. If a person initially had a 10 percent risk of developing dementia, that risk would be heightened to 13 percent by taking one of these drugs, according to this study. That risk is still much lower than many other modifiable risk factors that patients can control, like smoking or physical inactivity, which are associated with a 40 to 60 percent higher risk.
This study was published in the British Medical Journal.