Common Medications May Increase Risk of Alzheimer's Disease

Medically Reviewed By William C. Lloyd III, MD, FACS
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You may take an antihistamine for your allergies or a sleeping pill to help you nod off at night. But did you know that these drugs may be linked to raising your risk of Alzheimer’s disease, especially if you are in a risk group for this condition?

Two main types of drugs have been associated with a greater risk of Alzheimer’s when used on an extended basis (longer than three months): anticholinergics and benzodiazepines (such as anti-anxiety and sleep medications). Learn more about these common medications and their potential to raise your Alzheimer’s risk.

What are anticholinergic drugs?

Anticholinergic drugs work in part by blocking the action of a neurotransmitter in your brain called acetylcholine, which promotes thinking, learning and memory, plus affects your nervous system. Some conditions that anticholinergic drugs treat include:

Examples of common anticholinergic drugs include:

  • Diphenhydramine (Benadryl), which is used as an antihistamine to treat allergies and as a sleep-inducer

  • Cyclobenzaprine (Flexeril), a muscle relaxant given to ease spasms

  • Scopolamine (Transderm Scop), applied as a transdermal patch to prevent motion sickness

  • Oxybutynin (Ditropan), an incontinence medication that quells overactive bladders

  • Amitriptyline (Elavil), one of several tricyclic antidepressants

Benzodiazepines work differently than anticholinergics. These drugs, which include anxiety medications like alprazolam (Xanax) and diazepam (Valium), boost a different neurotransmitter, gamma-aminobutyric acid, or GABA, which slows the activity of neurons in the brain. This action makes it easier to relax and sleep.

What does research show about these drugs’ Alzheimer’s risk?

A variety of studies have observed the association between drug use and development of Alzheimer’s or dementia in general, especially among older people and those who have risk factors for the disease.

Anticholinergics

Here are the findings:

  • One large study by the University of Washington published in 2019 tracked participants aged 65 and up in a seven-year study (Adult Changes in Thought). The study recorded the participants’ drug use for 10 years prior to the study’s start. The researchers discovered that those who took an anticholinergic drug for three years or more had a 54% higher dementia risk than someone who took the same dose for three months or less.

  • A large study by English researchers published in 2019 found that people older than 55 who took anticholinergics daily for three years had a 50% higher risk of developing dementia.

  • A 2020 study of 688 older men and women (average age 74) led by researchers at the University of San Diego School of Medicine found that those taking at least one anticholinergic drug were 47% more likely to develop mild cognitive impairment (often a precursor to Alzheimer’s and other forms of dementia) over a 10-year period than non-users. People with risk factors for Alzheimer’s, such as genes linked to the disease or Alzheimer’s biomarkers in their cerebrospinal fluid, were at especially high risk of developing cognitive impairment. 

Benzodiazepines

Another study by French and Canadian researchers looked at the effect of benzodiazepines. This study compared people older than 66 who had been diagnosed with Alzheimer’s to people of the same gender and age who did not have Alzheimer’s. Looking at their prescriptions in the 5 to 6 years before the Alzheimer’s diagnosis, researchers found that those who had taken benzodiazepines for 3 to 6 months had a 32% greater risk of Alzheimer’s disease, compared to those who had never taken them. Those who had taken the drugs for more than six months had an 84% higher risk. Long-acting benzodiazepines, such as diazepam (Valium) and flurazepam (Dalmane), carried a higher risk than short-acting drugs, such as lorazepam (Ativan) and alprazolam (Xanax).

Why do these drugs have such an impact? Researchers say that drugs in general affect older people more strongly than younger populations. As we age, our kidneys and liver become less efficient at clearing drugs from our bloodstream. Drugs also are stored in body fat, which we tend to accumulate as we get older. Older people also may take multiple medications, including more than one anticholinergic, potentially causing a more significant impact. Alzheimer’s itself depletes acetylcholine, the neurotransmitter that is blocked by anticholinergics, so taking these drugs can be a double hit to an area of the brain that regulates memory.

What should you do if you take these drugs?

Keep in mind that the research shows associations and correlations—not causation or definitive proof.

However, if you are an older person or have Alzheimer’s risk factors, it’s a good idea to talk with your doctor about your medications. Are there non-anticholinergic medications you can take instead? Do the benefits of your medication outweigh its risks? Perhaps you can revisit beneficial lifestyle habits to help control your symptoms.

Another question to ask is if you are taking the lowest possible effective dose. The researchers at the University of California in San Diego found that the older people in the study were taking much higher doses of anticholinergic drugs than recommended for their ages. The majority (57%) were taking double the recommended dosage and 18% were taking four times the optimal dose. One first step might be to find out if you are taking too high a dose; another would be to see how many anticholinergic drugs you are taking to see your total intake.

A doctor in England has created an online tool, the “Anticholinergic burden calculator,” where you can plug in what drugs you are taking and see how they combine. If you have a score of three or higher on this calculator, you are considered at higher risk of developing cognitive impairment.

Talk with your doctor first before stopping any medications. Severe side effects are possible for some medications, if you stop them cold turkey. Your doctor should be open to a discussion with you about anticholinergics as well as benzodiazepine use, to see whether they raise your risk of Alzheimer’s disease and if there are changes you can make to reduce this risk.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Jun 2
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