Mounting scientific research links popular over-the-counter and prescription medications taken by millions of Americans to a significantly increased risk of cognitive decline and dementia.
An estimated one in five Americans regularly uses an anticholinergic drug, a broad category of medicines that includes common allergy remedies, nighttime sleep aids, bladder control treatments, and antidepressants.
Alicia Brown, 57, a nurse and healthcare administrator who works with dementia patients, relied on diphenhydramine, the antihistamine in Benadryl, to fall asleep for 15 years. Brown would take nighttime cough or allergy medication once every six weeks for a few days to get five hours of sleep during episodes of debilitating insomnia, saying: "It helped shut off my brain, and if I did that, I could get a good five hours."
After discovering research connecting diphenhydramine to cognitive decline earlier this year, Brown stopped taking the medication eight months ago. With a mother living with dementia and daily professional exposure to the condition, Brown felt continuing her sleep aid was no longer an option.
"I see the impact daily of people living with dementia," Brown told the Daily Mail. "The risk of of these medicines is not worth it. Losing who you are, who you were, your memories, your relationships, it is devastating. If I can do something to avoid a greater risk, I'm definitely going to do that."
She has since transitioned to non-medicinal sleep strategies, including keeping her bedroom cooler and darker, using white noise, and trying essential oil blends and herbal patches. "They are nowhere near as effective, despite some people swearing by them," Brown said. "They don't quiet the 'noise' that keeps me awake - the constant replay of the day, organizing what is coming during the week, the grocery list for Mom, all of those typical things."
"Whatever I need to do since anticholinergics are just something I'm not willing to risk unless the science eventually points away from it being an issue," she added. "I'm going to find other options."
Anticholinergic drugs in common household remedies
Anticholinergic properties are present in more than 600 prescription and over-the-counter medications. Over-the-counter options include diphenhydramine in Benadryl, doxylamine in Unisom SleepTabs, dimenhydrinate in Dramamine, meclizine in Bonine, and nighttime products such as Tylenol PM, Advil PM, and ZzzQuil.
Prescription anticholinergics include bladder medications oxybutynin (Ditropan), tolterodine (Detrol), and solifenacin (Vesicare); antidepressants amitriptyline (Elavil), nortriptyline (Pamelor), and paroxetine (Paxil); Parkinson's symptom treatments procyclidine (Kemadrin) and benztropine; bowel medication dicyclomine (Bentyl); and antipsychotics clozapine (Clozaril), olanzapine (Zyprexa), and quetiapine (Seroquel).
Benadryl parent company Kenvue told the Daily Mail in a statement: "The health and safety of consumers is our top priority. Diphenhydramine-containing medicines have a long history of safe and effective use when taken as directed. Based on our review of available evidence, we have not found that diphenhydramine increases dementia risk when used as directed on the label. We will continue to evaluate safety information on an ongoing basis as part of our commitment to consumer safety."
How anticholinergics affect brain function
Anticholinergics work by blocking acetylcholine, a chemical messenger used by the nervous system to control bodily functions, including bladder activity, nausea, allergy symptoms, and drowsiness. In the brain, acetylcholine plays a crucial role in communication between cells involved in memory, attention, and executive function.
By blocking acetylcholine in the brain, these drugs can interfere with cell communication, which experts believe increases the risk of cognitive decline. Each year, more than 500,000 Americans are diagnosed with mild cognitive impairment (MCI), and around one in five will progress to dementia within a year.
While doctors attribute up to 40 percent of dementia cases to preventable risk factors like smoking, heavy drinking, physical inactivity, obesity, high blood pressure, diabetes, hearing loss, and social isolation, experts warn that regular medication use represents another potential hazard hiding in plain sight.
Scientific studies reveal rising dementia risks
Numerous studies indicate that cumulative exposure to anticholinergics increases cognitive risk. One study found older adults taking anticholinergic drugs had a 47 percent greater risk of developing mild cognitive impairment. A 2020 analysis pooling data from nearly 650,000 patients across five countries associated long-term use with a 46 percent higher risk of dementia, while a 2025 review of over 3.6 million patients found a 20 percent increased risk among people taking anticholinergics for bladder problems.
A separate major study of more than 280,000 people aged 55 and over also linked long-term exposure to certain anticholinergics with higher dementia risk. Additionally, trial data tracking carriers of the APOE4 Alzheimer's gene showed that APOE4 carriers taking anticholinergics experienced a steeper decline in memory over 36 months than non-users without the allele, while non-carriers on the drugs and carriers off them declined less sharply.
Dr John La Puma, a California-based internal medicine physician and author, told the Daily Mail: "I actively de-prescribe these, as most people don't need them and they are hazardous to many older people." Dr La Puma added: "There is a cumulative, dose-dependent association with higher dementia or MCI risk. There is also, especially for people most at risk, imaging evidence of real brain change."
Dr Parth Bhavsar, family medicine physician and medical director at TeleDirectMD, told the Daily Mail: "We know that strong anticholinergics may cause confusion and memory problems, especially in older people. The issue is how exposure over the years contributes to neurodegeneration and makes it faster, if the brain is predisposed or partially represents an underlying condition."
Widespread use and medical recommendations
It remains unclear whether long-term brain damage from anticholinergics can be reversed. Short-term memory and thinking problems may improve once the medications are stopped, but scientists do not yet know whether years of exposure cause lasting brain changes or whether elevated dementia risks eventually return to normal.
Understanding the full scale of exposure is complicated because many anticholinergics are sold over the counter, meaning prescription records underestimate total use. Estimates suggest up to 43 percent of older adults and 26 percent of younger adults regularly take medications with anticholinergic effects.
Dr Michael DeShields, a New Jersey-based internal medicine physician, told the Daily Mail: "Many older adult patients are using multiple anticholinergic medications such as diphenhydramine for sleep, bladder antispasmodic agents, muscle relaxants and older generation antidepressants."
To reduce potential risks, Dr DeShields said it would be safer to reduce unnecessary anticholinergic use where possible. He advised patients concerned about cognitive decline to speak with their prescribing physician about switching to an alternative medication.
