The Drug in Question: What Diphenhydramine Actually Is
Diphenhydramine belongs to two classes of medications: antihistamines and anticholinergics. It was originally developed to treat allergic reactions, but its strong sedative effect made it a go-to ingredient for nighttime sleep formulas. Today it shows up in dozens of recognizable products, from Benadryl to Advil PM to ZzzQuil.
Over-the-counter antihistamines are frequently used for sleep because they are inexpensive and readily available, but they have limited data on safety and efficacy when used for insomnia. Diphenhydramine is the most commonly used OTC pharmacologic agent. That accessibility is part of the problem. Easy availability tends to make a drug feel routine, and routine use is exactly what raises concern for older patients.
Why It’s on the Medical Watchlist for Older Adults
Diphenhydramine and doxylamine, the two antihistamines found in nearly every OTC sleep product, are on the American Geriatrics Society’s Beers Criteria list of medications that older adults should avoid. The reason is their anticholinergic effect: they block a brain chemical called acetylcholine that plays a central role in memory and alertness.
The Beers Criteria, developed by the American Geriatrics Society, specifically recommends avoiding diphenhydramine in people 65 and older. This is not a minor advisory footnote. The Beers Criteria is widely regarded as the gold standard reference for medication safety in older adults, and diphenhydramine’s placement on that list reflects consistent concern across the medical community.
The Aging Brain Is More Vulnerable Than You Might Expect
Older adults are especially vulnerable because the brain produces less acetylcholine with age, and the blood-brain barrier becomes more permeable, letting more of the drug reach sensitive tissue. In practical terms, the same dose that causes mild drowsiness in a younger person can cause significant confusion or cognitive disruption in someone over 65.
Diphenhydramine has strong anticholinergic effects that older adults metabolize more slowly, raising the risk of dementia, daytime drowsiness, falls, confusion, and urinary retention. Slower metabolism means the drug lingers in the body far longer than the label implies, leaving residual effects that stretch well into the following day.
The Dementia Question: What the Research Shows
Research suggests a possible link between long-term use of diphenhydramine and an increased risk of dementia in older adults. One study followed nearly 3,500 adults aged 65 and older for more than 10 years, with all participants free of dementia at the start. The findings that emerged were not reassuring.
A four-year French population-based cohort study of nearly 6,912 participants demonstrated that continuous anticholinergic drug use increases dementia risk by 65 percent. A landmark study published in JAMA Internal Medicine followed over 3,000 adults for more than seven years and found that people aged 65 and older who took strong anticholinergic medications daily for at least three years had a significantly higher risk of developing dementia. Diphenhydramine was one of the primary culprits.
It is important to note that while these studies show a correlation, they do not definitively prove causation. Still, the volume and consistency of the data has led most geriatric specialists to treat the concern as more than theoretical.
Short-Term Side Effects That Pose Real Dangers
Sleeping pills have special risks for older adults. The drugs can stay in your body longer and cause side effects like confusion, memory issues, and balance problems that can increase the risk of falls and hip fractures. These are not rare edge cases. They represent common, documented outcomes in clinical settings.
Older adults who take OTC medications marketed as sleep aids or “PM” pain relievers containing diphenhydramine may experience side effects such as mental confusion, bladder disturbances, and bowel disturbances. For someone already managing multiple health conditions, adding those effects to the mix can quickly become a serious problem.
The Delirium Risk in Hospital Settings
An analysis published in the Journal of the American Geriatrics Society reveals that older inpatients admitted by physicians who prescribe higher amounts of first-generation antihistamines face an elevated risk of delirium while in the hospital. This finding is particularly striking because it reflects what happens even during relatively brief, supervised exposure to the drug.
First-generation antihistamines, such as diphenhydramine, are among the leading causes of medication-related harms in older adults. Older hospitalized patients exposed to higher prescribing rates of these medications have a 41 percent increased odds of developing delirium during admission. Delirium in hospitalized elderly patients is associated with longer stays and worse long-term outcomes.
The “PM” Label Problem
Many people assume that if a medicine is sold over the counter, it must be safe. For older adults, that is not always true. The familiar “PM” branding on products like Tylenol PM, Advil PM, or Aleve PM tends to read as mild and routine, not as a warning to proceed carefully.
Patients who are 55 or older may want to avoid regular or long-term use of anticholinergics and sleeping pills. Diphenhydramine is both an anticholinergic and a sleeping pill, which makes it of even greater concern. The combination of both classifications in one widely available tablet is something most consumers never consider when reaching for a box off the shelf.
Tolerance Develops Faster Than Most People Realize
The first goal of drug therapy for sleep problems should be modest improvement rather than a total cure. Sleeping pills are a temporary solution and should be reduced and then stopped after two to three weeks under a doctor’s care. Yet many older adults continue using them far longer than that, often because stopping is harder than starting.
Rebound insomnia, which is insomnia that returns after sleeping pills are abruptly stopped, is a real phenomenon. Some people need to gradually withdraw from sleeping pills to avoid it. This cycle of dependency can quietly extend what was supposed to be a short-term solution into months or even years of continued use.
What Doctors Recommend Instead
Cognitive behavioral therapy for insomnia is the gold standard for treating insomnia in all populations. CBT-I improves sleep among middle-aged and older adults without comorbidities, as well as among patients with psychiatric and medical comorbidities. Importantly, CBT-I has more durable benefits than hypnotic medications among midlife and older adults.
Studies show that roughly 70 to 80 percent of seniors experience significant sleep improvements through CBT-I without side effects. If medication is truly needed, safer alternatives exist, including melatonin, low-dose doxepin, and ramelteon. These options carry meaningfully lower anticholinergic burdens and are generally better tolerated in older patients.
What to Do If You’re Already Using It
Diphenhydramine’s anticholinergic effects can cause sedation, confusion, and impaired balance, all of which pose meaningful concerns for older individuals who may already face a higher risk of falls or existing cognitive vulnerability. If you or someone you care for is using a “PM” sleep product regularly, it’s worth taking that seriously rather than assuming it’s harmless because it’s sold without a prescription.
Many geriatric care specialists advise older adults to avoid diphenhydramine unless specifically directed by a physician, and to ask about alternative medications with a lower anticholinergic burden when possible. If you are already taking a prescription sleep aid, do not stop it suddenly on your own. Talk with your doctor about whether it is still right for you and whether there are safer options.
The Bigger Picture on Sleep and Aging
Sleep quality significantly impacts overall health, especially in older adults, who often face comorbid conditions and polypharmacy, meaning the intake of five or more medications per day. These factors are common among those with sleep disorders. Adding a drug like diphenhydramine on top of an already complex medication regimen introduces additional interaction risks that can be difficult to predict.
People age 65 and older should typically try nondrug treatments first because there may be safer ways to improve sleep. That is not a vague suggestion. It reflects a clear, evidence-based consensus across geriatric medicine that reaching for a pill, especially an over-the-counter antihistamine, should not be the first response to a restless night.
The Takeaway
The appeal of diphenhydramine is understandable. It’s cheap, it’s quick, and it genuinely does make people feel drowsy. For a healthy adult dealing with one bad night, that might not be a serious concern. For older adults using it regularly, the calculus is very different.
The evidence connecting long-term use of this drug to cognitive decline, falls, confusion, and delirium in people over 65 is consistent enough that major medical organizations have put it on their avoid lists. That kind of consensus across geriatric medicine doesn’t happen lightly. A conversation with a doctor, specifically about sleep, is a far better starting point than a late-night trip to the pharmacy aisle.
AI Disclaimer: This article was created with the assistance of AI tools and reviewed by a human editor.