I have gotten many questions about news reports that some common drugs raise your risk for dementia. The stories are about anticholinergic drugs, a class of drugs that includes some popular brands of over-the-counter antihistamines as well as some prescription antidepressants and muscle relaxers. These drugs are taken regularly by about 20 percent of older people. A study followed 3434 older adults (average age 73 years) who had their cumulative dose of anticholinergic drugs calculated from pharmacy records for 10 years and then were screened for dementia every two years (JAMA Internal Medicine, January 26, 2016 and March 2015;175(3):401-7). Over the seven years of screening, 797 participants (23.2 percent) developed dementia. Participants who took even low doses, long term, of the drugs suffered increased risk for dementia, and the higher the dose and the longer people took them, the greater the risk. The authors emphasize that they have not shown that these drugs cause dementia, only that there is an association between taking the drugs and increased risk for dementia.
The same authors showed that people who take high doses of an opioid narcotic or nonsteroidal anti-inflammatory drugs (NSAIDs) are also at increased risk for dementia (J Am Geriatr Soc, 2015 Aug;63(8):1519-26). Their results contradict previous reviews that showed no association between opioid drugs and dementia (Rev Assoc Med Bras, 2008 Nov-Dec;54(6):529-36) or antihistamines and dementia (J Am Geriatr Soc, Feb 2011;59(2):251-7).
What are Anticholinergic Drugs? Anticholinergic drugs include antihistamines such as diphenhydramine (Benadryl) and chlorphinaramine to treat insomnia and allergies; oxybutynin and tolterodine for overactive bladder, and tricyclic antidepressants such as doxepin or amitriptyline for depression, migraine and pain.
Anticholinergic drugs block acetylcholine that sends messages from one nerve to another. Acetylcholine transmits messages for the parasympathetic system that moves smooth muscles in the gastrointestinal, urinary, and pulmonary tracts. They are often used to treat:
• gastrointestinal disorders (gastritis, diarrhea, pylorospasm, diverticulitis, ulcerative colitis, nausea, vomiting)
• genitourinary disorders (cystitis, urethritis, prostatitis)
• respiratory disorders (allergies, asthma, chronic bronchitis)
• slow heart rate due to an overactive vagus nerve
Common side effects of anticholinergic drugs include drowsiness, confusion, dry mouth, constipation or urinary retention.
My Recommendations This study does not suggest that you should stop taking your medications, but 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 over-the-counter medications for annoying but not unbearable symptoms, always ask yourself if the benefits of the pill exceed its potential side effects. Unfortunately, none of us know the real answer to that question.
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