If you look inside your medicine cabinet, there’s likely some good news and bad news when it comes to brain health. A few common medications, like statins or drugs to treat high blood pressure, appear to help lower the risk for dementia. But others, including some you can buy over the counter, may increase the risk.
Most of the research conducted has been observational, so it’s possible that factors other than the medications could explain the association with dementia. (Remember, correlation doesn’t always equal causation.) But there are a few drugs that experts think could be negatively affecting brain health more directly.
Antihistamines
The class of medications with perhaps the most evidence of raising dementia risk are called anticholinergics. They work by blocking the activity of the neurochemical acetylcholine, which is important for attention and memory.
Antihistamines, which are used as allergy medications and over-the-counter sleep aids, are one of the most common types. Other varieties are prescribed to treat depression and bladder issues, among other things.
In the short term, anticholinergics can cause drowsiness and memory impairment. In the long term, several studies suggest they can increase dementia risk by roughly 50 percent.
The greatest risk is among people who take this type of medication daily for multiple years, said Shelly Gray, a professor at the University of Washington School of Pharmacy.
“That once-in-a-while use of Benadryl is unlikely to increase risk for dementia,” Dr. Gray said. However, she noted that the American Geriatrics Society recommends older adults avoid antihistamines because the medications can also cause falls. As a result, she advised that people look for alternatives whenever possible.
So-called second generation antihistamines, like Claritin and Zyrtec, don’t have anticholinergic activity, so they can be a safer option for seasonal allergies, Dr. Gray said. If you struggle with insomnia, consider talking to a doctor about C.B.T.-I. or other potential treatments in place of medications like ZzzQuil or Unisom.
Antipsychotic Drugs
With mental health medications and dementia, there is a chicken-or-egg question: Do the drugs themselves increase the risk of dementia, or is it the conditions the drugs are prescribed for, such as depression or psychosis, that increase it? Or could the conditions even be early signs of the disease?
A few studies have indicated that antipsychotics are associated with an increased risk of dementia. There is also research linking the drugs to cognitive impairment in middle-aged users. And people with dementia prescribed antipsychotics to help manage psychiatric symptoms have an increased risk of death.
Taken together, these findings suggest the drugs may have a direct negative impact on the brain.
If people are prescribed these drugs for a condition like schizophrenia, then they should certainly take them, since the immediate need for treatment outweighs the potential long-term risk, said David Llewellyn, a professor of clinical epidemiology and digital health at the University of Exeter Medical School in England. But he said there’s been “a big push to reduce the prescription of antipsychotics in order to manage behavior” in people with dementia.
Benzodiazepines
These mental health medications, which work on a specific neurotransmitter to suppress brain activity, have also been linked to dementia. The American Geriatrics Society recommends older adults avoid benzodiazepines because they can increase the risk of cognitive impairment, delirium and falls.
However, sleep issues and anxiety — two of the most common reasons for a benzodiazepine prescription — can both increase the risk of cognitive impairment or be early signs of dementia. Indeed, a few recent studies suggest it may be these underlying health issues, not the medication, that’s behind the association.
To try to disentangle the cause and effect, Geoffrey Joyce, a professor of pharmaceutical and health economics at the University of Southern California, ran an analysis where he only looked at people who were prescribed benzodiazepines for back pain, which is not associated with dementia. He found no relationship between prescriptions for the medication and dementia diagnoses.
Dr. Joyce said that doesn’t definitively prove that benzodiazepines don’t increase dementia risk, but “it stemmed the tide” of concern. “All we would conclude is: We don’t see that. It needs further study,” he added.
Proton Pump Inhibitors
Conflicting evidence has also been reported about proton pump inhibitors, which are often used to treat acid reflux. Some studies found they increased the risk of dementia, while other research did not.
It’s unclear why drugs that act on stomach acid would affect the brain. One theory is that they can cause a deficiency in vitamin B12, which is linked to cognitive impairment.
It’s also possible that the connection is an artifact of incomplete data. Some proton pump inhibitors, like Prilosec, are purchased over the counter, so their use can be more difficult to track and analyze than prescription medications.
One of the few clinical trials that looked at dementia and proton pump inhibitor use, comparing a drug called pantoprazole and a placebo in older adults, did not see an increased dementia risk over the course of three years.
Dana G. Smith is a Times reporter covering personal health, particularly aging and brain health.
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