A new study in a peer-reviewed journal suggests that a type of drug commonly prescribed to treat depression, epilepsy, Parkinson's, and other ailments raises the risk of dementia. The study found that those who take strong anticholinergics daily for at least three years have 50% greater odds of developing dementia, according to the study in JAMA Internal Medicine. No significant risk was seen with weaker anticholinergics, such as those used as antihistamines (Benadryl) or for gastrointestinal disorders, reports WebMD. The study—based on data from more than 284,000 people age 55 and older between 2004 and 2016 in the UK—is observational, meaning it's not saying the drugs cause dementia, only that researchers see a link between their use and dementia cases.
"The study is important because it strengthens a growing body of evidence showing that strong anticholinergic drugs have long term associations with dementia risk," says study author Carol Coupland of the University of Nottingham, per CNN. Researchers already knew that anticholinergics can cause short-term side effects such as confusion, but this study takes a longer view. Anticholinergics help relax and contract muscles by blocking the chemical acetylcholine, explains WebMD. Those with the strongest link to dementia were antidepressants, bladder antimuscarinic drugs, Parkinson's drugs, and epilepsy drugs. No notable risk was seen for anticholinergics used as antihistamines, skeletal muscle relaxants, gastrointestinal antispasmodics, antiarrhythmics, or antimuscarinic bronchodilators. (A new form of dementia was just discovered.)