Study: Common Allergy Drugs Can Damage Brain, Increase Dementia Risk

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From allergies to insomnia, there's a pill for just about every problem. Problem is, those pills often come with a lengthy list of potential side effects.

And in the quest to cure what ails us as quickly as possible,  we tend to often overlook those warnings.

A new study offers the most definite proof yet of what scientists have known for at least a decade: Anticholinergic drugs are linked with cognitive impairment and an increased risk of dementia.

Even though you may not have heard the term 'anticholinergic,' you know the names of medications in this class of drug.

Names like Benadryl, Demerol, Dimetapp, Dramamine, Paxil, Unisom and VESIcare.

They're sold over the counter and by prescription as sleep aids and for chronic diseases.

Using brain imaging techniques, researchers at the Indiana University School of Medicine found lower metabolism and reduced brain sizes among study participants taking anticholinergic drugs.

"These findings provide us with a much better understanding of how this class of drugs may act upon the brain in ways that might raise the risk of cognitive impairment and dementia," said Shannon Risacher, an assistant professor of radiology and imaging sciences.

The study looked at 451 people, with an average age of 73. Sixty of them were taking at least one medication with medium or high anticholinergic activity. To identify physical and physiological changes that could be associated with the reported effects, researchers assessed the results of memory and cognitive tests; PET scans, to measure brain metabolism; and MRI scans, to assess brain structure.

The cognitive tests revealed that people taking anticholinergic drugs performed worse on short-term memory tests and some tests of executive function, including verbal reasoning, planning and problem-solving.

Anticholinergic drug users also showed lower levels of glucose metabolism -- a biomarker for brain activity -- both in the brain overall and in the hippocampus, a region of the brain associated with memory and which has been identified as affected early by Alzheimer's disease. The participants using anticholinergic drugs were also found to have reduced brain volume and larger ventricles, the cavities inside the brain.

A 2013 study by scientists at the Indiana University Center for Aging Research found that drugs with a strong anticholinergic effect cause cognitive problems when taken continuously for as few as 60 days. Drugs with a weaker effect could cause impairment within 90 days.

Never start or stop taking a medication without first consulting your doctor.