A study of 58,769 patients over 55 years of age diagnosed with dementia and 225,574 people of the same age without dementia found a 50 percent increased risk of dementia among people who used a strong anticholinergic drug daily for about three years within the 10-year study period (JAMA Intern Med, published online June 24, 2019). Anticholinergic drugs include:
• antidepressants (paroxetine-Paxil)
• anti-Parkinson’s drugs
• antipsychotic drugs (clozapine)
• urinary bladder relaxers (Enablex)
• some anti-nausea drugs (scopolamine), anti-asthma drugs (ipratropium), muscle relaxants (tizanidine), antihistamines (diphenhydramine-Benadryl), and anti-seizure drugs.
The association was stronger for antidepressants, bladder drugs, antipsychotics and epilepsy medications. The researchers did not find any increased risk of dementia with most antihistamines, bronchodilators, muscle relaxants or medications for stomach spasms or irregular heartbeats. This study supports others that show similar results (JAMA Intern Med, 2015;175(3):401-407).
Anticholinergics can block acetylcholine, a chemical that sends messages from one nerve to another to move muscles, increase heart rate, widen blood vessels, open bronchial tubes, and control intestinal muscles. They can block acetylcholine in the brain to decrease learning and memory (BMC Geriatrics, March 15, 2015;15(31)).
These studies suggest that anticholinergic drugs are associated with dementia; they do not prove that they cause dementia. However, the drugs only help to control symptoms and do not cure any of the diseases. If you take anticholinergic drugs regularly, talk to your doctor about taking other types of drugs that do not block acetylcholine, such as the antidepressants Celexa and Prozac.
A second major class of prescription drugs that have been associated with increased risk for dementia in people over 55 are the benzodiazepines, which are often used to treat anxiety and to help people sleep. Benzodiazepines increase the effects of gamma-aminobutyric acid (GABA), which slows messages across brain circuits. Researchers showed that people who took benzodiazepines for three to six months had a 32 percent greater risk of developing Alzheimer's disease, and those who took them for more than six months had an 84 percent greater risk than those who hadn't taken any (BMJ, April 25, 2018; 361;k1315). The long-acting benzodiazepines, diazepam (Valium) or flurazepam (Dalmane), were associated with greater risk than the shorter-acting drugs, triazolam (Halcion), lorazepam (Ativan), alprazolam (Xanax), or temazepam (Restoril).
These studies show that some prescription drugs are associated with increased risk for dementia, but they do not prove that they cause it. Discuss with your doctor the benefits as well as the side effects of all of your drugs. I believe that you should always work with your doctor to limit your current medications to those that are necessary. Realize that every pill that you take can have side effects or long term consequences, even if those effects have not yet been reported. Particularly if you choose to take prescription drugs or over-the-counter medications for annoying but not unbearable symptoms, always ask yourself if the benefits of the pill exceed its potential side effects. For example, if you are taking one of these drugs to help you urinate, you may decide that you are better off taking an extra 10 minutes to urinate instead. However, do not ever just stop taking prescription drugs on your own as you can be harmed by suddenly stopping them. Check with your doctor.