Could your antihistamine increase your risk for dementia?

A large study, recently published in JAMA Internal Medicine and conducted by our team of researchers at Kaiser Permanente Washington Health Research Institute (KPWHRI) and the University of Washington, confirmed a link between certain drugs and a significantly increased risk for developing dementia or Alzheimer’s disease. These drugs, called “anticholinergic” drugs, include over-the-counter drugs such as Benadryl and common prescription drugs taken for insomnia, urinary incontinence, and depression.

The population-based study analyzed data from more than 3,000 participants in GHRI’s long running Adult Changes in Thought study.

Alzheimer’s is a disease many people fear developing. One survey, which asked respondents which of seven diseases they feared most, found Alzheimer’s and cancer at the top the list, which could explain the widespread media attention following publication of this study.

Which drugs are “anticholinergic”

Acetylcholine is a neurotransmitter that sends signals in the nervous system. Anticholinergic drugs block these signals in the body and the brain. Side effects from the drugs can include drowsiness, constipation, difficulty urinating, and dry mouth and eyes.

Some specific anticholinergic drugs are:

  • Older antidepressants like doxepin (brand name Sinequan)
  • Antimuscarinics for bladder control like oxybutynin (Ditropan)
  • First generation antihistamines like diphenhydramine (Benadryl) and chlorpheniramine (Chlor-Trimeton). Drugs with diphenhydramine are also often taken as a sleep aid.

What should I do if I’m taking one of these drugs?

If you are taking any of these drugs or another drug that you believe is an anticholinergic drug, it’s important that you don’t just stop taking it, especially if it’s been prescribed by your health provider.

Instead, have a conversation with your doctor about the medication. It may be that another drug can be substituted, or that lifestyle changes can effectively address the issue for which you’re taking the drug. We also found that the dementia risk occurred in those taking anticholinergic drugs in higher amounts, often every day.

You can also read more about how to balance the risks and benefits of these common medications.

By Eric Larson, MD, MPH
Executive director, Kaiser Permanente Washington Health Research Institute