Several common medication classes can worsen cognitive function in people with dementia or increase the risk of cognitive decline in older adults. The most consistently harmful are anticholinergic drugs, which block a brain chemical essential for memory and thinking. But the list extends to certain sedatives, antipsychotics, corticosteroids, and some overactive bladder medications. Some of these are available over the counter, which makes them easy to take without realizing the risk.
Anticholinergic Drugs Pose the Biggest Risk
Anticholinergic medications work by blocking acetylcholine, a chemical messenger that plays a central role in memory, learning, and attention. In a healthy brain, reducing acetylcholine activity causes temporary fogginess. In a brain already affected by dementia, where acetylcholine levels are already low, blocking what remains can significantly worsen symptoms.
The tricky part is that anticholinergic properties show up in drugs prescribed for completely unrelated conditions. Certain antihistamines, antidepressants, bladder medications, and gastrointestinal drugs all have anticholinergic effects. A large study published in JAMA Internal Medicine confirmed that the drugs most strongly linked to dementia risk are those that block a specific type of acetylcholine receptor called the muscarinic receptor. These medications are found across many categories in your medicine cabinet, which is why they’re easy to overlook.
The American Geriatrics Society maintains a list called the Beers Criteria, updated most recently in 2023, that flags medications typically best avoided by adults 65 and older. Anticholinergic drugs feature prominently on that list, particularly for people with existing cognitive impairment.
Over-the-Counter Antihistamines and Sleep Aids
First-generation antihistamines like diphenhydramine (the active ingredient in Benadryl and many PM-branded painkillers and sleep aids) are strongly anticholinergic. Because these are sold without a prescription and marketed as harmless sleep helpers, many older adults take them regularly without considering the cognitive cost. The sedation you feel from these drugs is partly caused by the same acetylcholine blockade that interferes with memory.
If you or a family member with dementia uses an over-the-counter sleep aid or allergy medication, checking the active ingredient is worth the effort. Newer antihistamines like cetirizine and loratadine have far less anticholinergic activity and are generally safer options for allergy relief.
Bladder Medications Vary Widely in Brain Effects
Overactive bladder drugs are among the most commonly prescribed anticholinergics in older adults, and they differ dramatically in how much they affect the brain. The key factor is whether the drug can cross the blood-brain barrier.
Oxybutynin is the worst offender. Animal studies show it has extensive penetration into the central nervous system. In a crossover trial involving older adults with mild cognitive impairment, oxybutynin caused significant decreases in attention and cognitive continuity compared with placebo over a 21-day period. Tolterodine and solifenacin also penetrate the brain to some degree, though solifenacin showed no detectable effect on cognition in the same trial.
On the safer end, trospium chloride has a molecular structure that makes it very unlikely to reach the brain. One study found it was completely undetectable in cerebrospinal fluid even when present in the bloodstream. A four-week trial in adults averaging 68 years old found no difference between trospium and placebo on memory testing or mental status scores. If bladder control is a real quality-of-life issue, the choice of which medication to use matters enormously for someone with dementia.
Antipsychotics Carry an FDA Black Box Warning
Antipsychotic medications are sometimes prescribed to manage agitation, aggression, or psychosis in people with dementia. They carry a boxed warning from the FDA, the agency’s most serious safety alert, for increased mortality in patients with dementia. The risks include stroke, excessive sedation, falls, and aspiration.
Quetiapine is one of the most widely prescribed antipsychotics in dementia care in North America. Its breakdown product in the body is actually a more potent blocker of acetylcholine receptors than the original drug itself, meaning it adds anticholinergic burden on top of its sedating effects. This double impact makes it particularly problematic for cognitive function, even as it may temporarily reduce behavioral symptoms.
Benzodiazepines and Z-Drugs: Nuanced Risk
The relationship between benzodiazepines (drugs like lorazepam, diazepam, and alprazolam) and dementia has been debated for years. Earlier meta-analyses suggested these drugs increased dementia risk, with pooled odds ratios ranging from 1.33 to 1.78. But more recent, methodologically stronger research has challenged that conclusion.
A large population-based study found that overall benzodiazepine use was not significantly associated with dementia risk compared to never using them. However, the picture isn’t entirely clean. High cumulative doses of anxiety-type benzodiazepines specifically did show a modest increase in risk, with a hazard ratio of 1.33. And when researchers looked at benzodiazepine use in the period leading up to a dementia diagnosis, they found higher risk estimates in ever-users, suggesting that some of the association may reflect early dementia symptoms being treated with these drugs rather than the drugs causing dementia.
A large Danish study using national health records concluded that neither benzodiazepines nor the related “Z-drugs” (zolpidem, zopiclone, zaleplon) appear to increase long-term dementia risk. That said, in someone who already has dementia, these drugs still cause real short-term problems: excessive sedation, confusion, falls, and respiratory suppression. They may not cause dementia, but they reliably make it look and feel worse while the drug is active.
Corticosteroids Can Mimic Dementia
Systemic corticosteroids like prednisone, prescribed for conditions ranging from asthma to autoimmune disease, can cause cognitive impairment that looks remarkably like dementia. Patients have experienced disorientation, disorganized speech, and significant deficits in attention, concentration, and verbal memory while taking doses of 20 to 100 mg of prednisone daily.
The cognitive effects are dose-dependent. Memory problems with verbal recall have been observed after as few as four to five days of treatment. Severe psychiatric side effects, including psychosis and mania, were uncommon at doses below 40 mg per day of prednisone (about 1.3% of patients) but jumped to 18.4% at doses above 80 mg per day. For someone already living with dementia, even moderate doses can cause a dramatic and frightening worsening of symptoms.
The good news is that corticosteroid-related cognitive changes are typically reversible once the medication is reduced or stopped. This makes it especially important to recognize the pattern rather than assuming the person’s dementia has suddenly progressed.
Proton Pump Inhibitors: Less Risk Than Feared
Proton pump inhibitors, widely used for acid reflux and stomach ulcers, generated concern after early studies suggested a link to dementia. The proposed mechanism made biological sense: long-term use can reduce absorption of vitamin B12, magnesium, and other nutrients important for brain health, and the drugs may cross the blood-brain barrier.
However, a meta-analysis of 11 observational studies involving nearly 643,000 participants found no significant correlation between PPI use and dementia risk. Multiple subsequent analyses have reached the same conclusion. While chronic nutrient deficiencies from long-term PPI use remain a legitimate health concern, the direct dementia link has not held up under rigorous study.
Delirium vs. Permanent Worsening
One critical distinction that families often miss is between medication-induced delirium and a true progression of dementia. Delirium comes on rapidly, sometimes within hours or days of starting or changing a medication. The person may become suddenly confused, agitated, or unusually drowsy, and their symptoms typically fluctuate throughout the day. This looks very different from dementia’s gradual decline, where memory and thinking skills stay relatively consistent from hour to hour.
People with early dementia usually stay alert and can maintain attention during a conversation. In delirium, that ability breaks down noticeably. The person may seem to drift in and out, become disoriented about where they are, or have trouble following a simple exchange.
The practical importance of recognizing delirium is that it’s often fixable. When medications are the cause, adjusting the dose or switching to an alternative may be all that’s needed. A sudden cognitive decline in someone with dementia should always prompt a medication review before anyone concludes the disease itself has worsened.