Anticholinergic burden refers to the total effect of medications that block a brain chemical called acetylcholine, which can cause memory problems, confusion, and increase the risk of dementia especially when taken long-term. Think of the last time you reached for an over-the-counter allergy pill or sleep aid. Harmless, right? Not quite. Some of the most commonly used OTC medications, including diphenhydramine (Benadryl) and doxylamine, carry a hidden danger: A potential link to cognitive decline and increased dementia risk.

For older adults, especially those over 50 or under the care of family members or caregivers, this is particularly concerning. As we age, our brains become more sensitive to these medications. Studies show that prolonged exposure can lead to memory loss, confusion, difficulty concentrating, and a significantly increased risk of dementia. If you're caring for an ageing parent or loved one, it's important to check their medicine cabinet not just for what they’re taking, but how often and for how long.

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What Are Anticholinergic Drugs and Why Are They Risky?

Anticholinergic drugs work by inhibiting the action of acetylcholine in the brain and body. They’re used to treat conditions like:

• Allergies
• Insomnia
• Motion sickness
• Bladder issues
• Depression (certain prescriptions)

However, acetylcholine plays a key role in cognitive function. Blocking it over extended periods, especially in older adults, can impair memory and increase the risk of Alzheimer's disease and dementia. Hence, being careful with what your elders are taking is vital. 

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The Evidence Is Mounting

1. Harvard Study (2015)

A landmark study published in JAMA Internal Medicine found that people aged 65 and older who used anticholinergic medications daily for three years or more had a 54 per cent higher risk of developing dementia than those who used them for less than 90 days.

2. UK Case-Control Study

Research from the UK’s QResearch database involving more than 280,000 participants linked high cumulative use of anticholinergics, particularly sleep aids and antihistamines, to a dose-dependent increase in dementia risk. 

3. National Geographic Analysis

Diphenhydramine (the active ingredient in Benadryl) was flagged in a 2024 National Geographic feature as one of the most problematic OTC anticholinergics, due to its strong brain-penetrating properties and widespread, unregulated use by adults for sleep and allergies. 

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Anticholinergic Burden: The Silent Accumulation

Your anticholinergic burden isn’t just about a single pill. It’s the cumulative effect of taking one or more medications with anticholinergic properties, often unknowingly, over months or years. Some drugs may have a mild anticholinergic effect, but when combined, the burden rises.

Doctors Are Concerned, Here’s Why

Geriatricians and neurologists have long warned against the routine use of first-generation antihistamines like diphenhydramine, particularly in older adults.

“Even occasional use of strong anticholinergic drugs can affect thinking and memory,” says Dr. Shelly Gray, a professor of pharmacy at the University of Washington and co-author of the ACT (Adult Changes in Thought) dementia study titled “Cumulative Use of Strong Anticholinergics and Incident Dementia: A Prospective Cohort Study”, published in JAMA Internal Medicine.

“If you’re over 60 and taking diphenhydramine or other anticholinergics regularly, it’s time to re-evaluate.”

These medications often appear harmless because they’re available without a prescription, but that doesn't mean they’re safe for long-term use, especially in ageing populations.

Are Your Elders Taking These Common OTC Anticholinergic Medications?

Check your labels for these active ingredients:

Safer Alternatives Exist

Thankfully, you can manage symptoms without compromising your loved ones cognitive health. Consider these safer, non-anticholinergic alternatives:

Also, talk to your doctor about deprescribing if you’re on multiple medications with anticholinergic effects.

How to Protect the Brain Health

• Review medications for your parents and elders regularly. Since the risk is high in elderly people.
• Limit OTC medication use beyond the short-term
• Use the Anticholinergic Cognitive Burden (ACB) Scale with the doctor to assess risk possibility with elders.
• Stay informed because what you think is “just an allergy med” could be silently putting your loved ones under dementia risk.

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Anticholinergic drugs aren’t inherently bad, but the way we use them, especially without awareness, can be. As more research reveals the long-term risks to brain health, it’s crucial we start treating OTC medications with the same caution as prescriptions.

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