An allergy pill before bed, an over-the-counter sleep aid, a bladder medication taken every day for years — many people take at least one drug with anticholinergic effects without ever hearing the term. Long-running studies have looked at what regular, long-term use of these medications might mean for the brain.
Large studies have linked higher cumulative use of strong anticholinergic medications — a category that includes certain antihistamines, older antidepressants, and bladder medications — to an increased risk of dementia, with risk rising alongside the dose and duration of use. Not every anticholinergic carries the same risk: some individual drugs within the same class show a much stronger association than others, and weaker anticholinergics appear far less concerning. Whether the added risk fully reverses after stopping the medication isn't settled — some evidence suggests part of it may persist. None of this means anticholinergic medications should be stopped abruptly; it's a reason for a medication review with a doctor or pharmacist, not a reason to panic.
What Counts as an Anticholinergic, and How Common Is It
Acetylcholine is a neurotransmitter involved in memory, attention, and muscle control. Anticholinergic drugs work by blocking its action — which is often exactly what makes them effective, whether that's drying up a runny nose, calming an overactive bladder, or easing symptoms of depression. In one of the largest cohort studies on this question, three drug categories accounted for most of the anticholinergic use researchers tracked: older-style antidepressants, first-generation antihistamines, and bladder medications used for urinary urgency. That first-generation antihistamine category includes a very familiar over-the-counter name: diphenhydramine, the active ingredient in Benadryl and in most "PM" sleep aids and nighttime pain relievers.
The Dose-Response Evidence
The most-cited study on this question followed a large group of older adults for a mean of 7.3 years, tracking anticholinergic medication use through pharmacy dispensing records rather than relying on participants' memory of what they'd taken. Compared with non-users, dementia risk rose in a clear step-pattern as cumulative anticholinergic exposure increased, reaching a 54% higher risk in the highest-use group — roughly the equivalent of a standard daily dose for more than three years — with a statistically significant trend linking more cumulative use to more risk. The researchers reported that this pattern held up across a range of additional checks built into the study design.
Not Every Anticholinergic Carries the Same Risk
Cumulative dose isn't the only variable that seems to matter — which specific drug someone takes appears to matter too. A large, more recent case-control study focused specifically on medications prescribed for an overactive bladder, comparing people who developed dementia against closely matched people who didn't. It found meaningfully higher dementia risk associated with oxybutynin, solifenacin, and tolterodine, while several other bladder medications in the same general drug class — including darifenacin, fesoterodine, and trospium — showed no significant increase in risk. That's a useful nuance: "anticholinergic" isn't one uniform risk category, and for some conditions, a lower-signal option within the same drug class may exist.
An honest limitation: these are observational studies, which can show an association but can't prove the medication itself caused the added risk. One open concern is reverse causation — early, undiagnosed dementia can itself cause symptoms like insomnia or urinary urgency that lead a doctor to prescribe an anticholinergic in the first place, which could make the medication look riskier than it actually is. Researchers have tried to account for this in various ways, but it can't be fully ruled out. It's also genuinely unclear whether the risk reverses after stopping: one commentary on this research pointed out that dementia risk looked similar for people with recent versus more distant heavy use, raising the possibility that some effects may not fully reverse — a question that hasn't yet been tested in a randomized trial.
What This Means for You
None of this is a reason to stop a prescribed medication on your own — for some anticholinergics, stopping abruptly can cause its own problems. It's a reasonable prompt for a conversation with your doctor or pharmacist, especially if you take one of these medications regularly or expect to for the long term.
- Ask for a full medication review, prescription and over-the-counter Bring a complete list, including anything you take only occasionally for allergies, sleep, or an upset stomach — a pharmacist can screen for cumulative "anticholinergic burden" across everything you take, not just one prescription at a time.
- Watch for hidden anticholinergics in OTC products Many nighttime and "PM" versions of pain relievers, allergy pills, and cold medicines contain diphenhydramine, even when the packaging emphasizes a different main ingredient.
- If you take a bladder medication long-term, ask about your specific options Research suggests risk may vary by the specific drug within the same class — worth raising directly with your doctor rather than assuming every option carries equal risk.
- Don't stop or switch anything without medical guidance A doctor can weigh the specific drug, dose, and duration against the condition it's treating, and manage any change safely if one makes sense.
The Bottom Line
Long-term, higher-dose use of strong anticholinergic medications is linked to a higher risk of dementia across multiple large studies, with risk rising alongside cumulative dose — and the specific drug matters, since some options in the same class show little to no signal at all. What's genuinely unresolved is whether this risk reverses after stopping, and these remain observational studies that can't fully rule out other explanations. The practical takeaway isn't to stop a medication on your own; it's to make sure your doctor or pharmacist has the full picture of everything you're taking, prescription and over-the-counter alike.
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Get the Free Brain Health Mastery BundleFrequently Asked Questions
What are anticholinergic drugs?
Anticholinergic drugs block the action of acetylcholine, a neurotransmitter involved in memory, attention, and muscle control. They're found in many prescription and over-the-counter medications, including certain antihistamines, antidepressants, and bladder medications, where blocking acetylcholine is what produces the intended effect — like drying up allergy symptoms or calming an overactive bladder.
Which common medications have anticholinergic effects?
The drug classes most studied for this risk include first-generation antihistamines like diphenhydramine (found in Benadryl and many "PM" sleep aids and pain relievers), certain older antidepressants such as amitriptyline and doxepin, and bladder medications like oxybutynin and tolterodine. Many of these are available without a prescription.
If I stop taking the medication, does the risk go away?
That's not yet settled. One analysis connected to a major cohort study found that dementia risk looked similar whether anticholinergic use was recent or had happened years earlier, which raised the possibility that some effects may not fully reverse after stopping. This question hasn't been tested in a randomized controlled trial, so it remains an open question rather than a settled answer.
Should I stop taking my anticholinergic medication because of this research?
Not on your own, and not abruptly. These findings come from observational studies, which can't prove the medication caused the risk, and for some anticholinergics, stopping suddenly can cause its own problems, such as withdrawal effects or the return of the condition being treated. The reasonable step is a full medication review with your doctor or pharmacist, who can weigh the specific drug, dose, and duration against your individual risks and benefits.
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