A growing body of research indicates that a class of common medications known as anticholinergics may be associated with an increased risk of dementia. These drugs, which include widely available over-the-counter remedies and several prescription medications, work by blocking the neurotransmitter acetylcholine. While effective for various conditions, including allergies, insomnia, and bladder control, blocking acetylcholine in the brain can interfere with memory and attention, potentially contributing to cognitive decline.
Millions of Americans use anticholinergic medications, with estimates suggesting that up to 43 percent of older adults and 26 percent of younger adults regularly take drugs with anticholinergic effects. Some studies have found a significant increase in the risk of developing mild cognitive impairment (MCI), a precursor to dementia, among older adults taking these medications. One analysis pooling data from nearly 650,000 patients found long-term anticholinergic use was associated with a 46 percent higher risk of dementia.
Diphenhydramine, the active ingredient in Benadryl and found in many nighttime sleep aids like Unisom, Tylenol PM, and Advil PM, is among the most commonly used anticholinergics that researchers are concerned about. Other prescription anticholinergics include drugs for overactive bladder such as oxybutynin and tolterodine, and antidepressants like amitriptyline and paroxetine.
Physicians warn that the danger appears to increase with prolonged daily use rather than occasional use. "There is a cumulative, dose-dependent association with higher dementia or MCI risk," said Dr. John La Puma, an internal medicine physician. "There is also, especially for people most at risk, imaging evidence of real brain change."
Alicia Brown, a nurse who has cared for dementia patients, stopped taking diphenhydramine for insomnia after 15 years due to concerns about its potential link to dementia. "The risk of these medicines is not worth it. Losing who you are, who you were, your memories, your relationships, it is devastating," she told the Daily Mail. Brown has since explored alternative sleep aids, noting they are less effective but a risk she is willing to take.
While researchers cannot definitively state that anticholinergics cause dementia, the association is a growing concern. Some experts suggest that older adults and those already experiencing cognitive issues may be particularly vulnerable. There is also a concern that individuals may be unknowingly taking multiple anticholinergic medications simultaneously, combining prescription drugs with over-the-counter products, which could amplify the risk. Physicians recommend discussing concerns about cognitive decline with a doctor to explore alternative treatments and reduce unnecessary anticholinergic use.
Kenvue, the parent company of Benadryl, stated that diphenhydramine-containing medicines have a long history of safe and effective use when taken as directed and that they have not found evidence that the drug increases dementia risk when used as labeled. They indicated they would continue to evaluate safety information.
The long-term effects and potential for lasting brain changes or elevated dementia risk after years of exposure are still under investigation. Doctors note that while short-term memory and thinking problems may improve after stopping these drugs, it is unclear if the damage can be fully reversed. Anticholinergic medications include a wide range of drugs, from common allergy and sleep aids to prescription medications for bladder control, depression, and Parkinson's symptoms. More than 600 prescription and over-the-counter medications are thought to possess anticholinergic properties.