If you're a senior citizen — and even if you're not — you may want to avoid some ordinary over-the-counter medications. A study by the Indiana University School of Medicine found that common drugs, including antihistamines and nighttime cold medicines that are probably sitting in your medicine cabinet, contain an anti-cholinergic ingredient. You may take them on a regular basis to treat minor ailments such as colds, flu, allergies, insomnia, motion sickness, and heartburn. But they can greatly increase your risk of dementia if you're older.
Study participants, who were in their early 70s, were part of a national Alzheimer's research project — The Alzheimer's Disease Neuroimaging Initiative — and the Indiana Memory and Aging Study. Researchers studied their brain function using a combination of MRI scans, PET scans, and memory and cognitive tests. They found that those who took anti-cholinergic drugs had smaller brains and larger cavities inside the brain, and performed worse on cognitive tests than those who didn't take the drugs.
The study also found that those who used anti-cholinergic drugs had lower levels of glucose metabolism, which is a biomarker for brain activity, throughout the brain and in the hippocampus, an area associated with memory that is affected early in the Alzheimer's process.
The scientists found more than 100 drugs that contain anti-cholinergic ingredients. These chemicals block acetylcholine, a neurotransmitter that transmits messages from nerve cells to other cells. In the brain, acetylcholine is important to learning and memory. In other areas of the body, it starts muscle contractions.
The anti-cholinergic ingredients in question in over-the-counter medicines are diphenhydramine and promethazine. They're used in common medicines, including Benadryl, Dimetapp, Dramamine, Midol PM, Motrin PM, Nytol, Unisom, and Zantac.
The study, which was published in the journal JAMA Neurology, wasn't the first to suggest that anti-cholinergic drugs affected the brain: Scientists have linked anti-cholinergic medications with thinking and memory problems in older adults for at least 10 years. Previous studies found that seniors who took the prescription drugs oxbutynin (treats overactive bladder) and doxepin (anti-depressant) often develop cognitive problems, including dementia.
A 2015 study reported in JAMA Internal Medicine found a strong link between long-term use of anti-cholinergic medications containing diphenhydramine (Benadryl) and dementia. A 2013 study involving almost 3,700 older adults found that brain function could change within two months of taking the drugs.
The brains of Alzheimer's patients are known to be deficient in acetylcholine, and researchers believe pills containing anti-cholinergic drugs make Alzheimer's worse, or even trigger the brain-robbing condition. A 2015 study found that taking some anti-cholinergic drugs for at least three years raised the risk of Alzheimer's by as much as 54 percent. The risk rose with how often the drugs were taken.
Many prescription medications also contain anti-cholinergic ingredients, including some tricyclic antidepressants, medications that relieve symptoms of Parkinson's, drugs to control overactive bladders, and liquid cough syrups.
"Given all the research evidence, physicians might want to consider alternatives to anti-cholinergic medications if available when working with their older patients," said researcher Shannon Risacher.
For a complete list of anti-cholinergic medications, go here.
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