Research links widely-used drugs to a nearly 50% higher risk of dementia

A recent study found some common drugs could increase the risk of dementia or dementia-like symptoms by nearly 50%. According to the research, published in JAMA Internal Medicine, discovered the increase odds of dementia in people 55 and older who take anticholinergic medications.

Anticholinergics are used to treat a wide range of conditions, including depression, symptoms of Parkinson's disease, bladder control and insomnia. An estimated 1 in 4 older adults take anticholinergic drugs. Some antihistamines like Benadryl are also anticholinergics, but were not associated with dementia in this study.

"This is a very broad class of medications," CBS News' Dr. Tara Narula told "CBS This Morning." "A lot of Americans use these drugs whether prescription or over-the-counter ranging from things like antihistamines or anti-allergy medicines, sleep aids, bladder control medication, Parkinson's drugs, COPD meds, I mean the list goes on and on."

The study, which Narula cautioned is a correlational and not a cause-and-effect study, looked at more than 200,000 individuals in Britain who took a strong anticholinergic drug for three years and found a 49% increased risk of dementia.

"A lot of these researchers have said, look, some of these drugs that we're giving — like the anti-depressants and the sleep aids — we're giving to people who may have had dementia all along because some of these things like depression and sleep deprivation are early signs of dementia," she said.

It's important for pharmacists, doctors and patients all be informed about this and to keep in mind that the elderly are particularly susceptible for a number of reasons including a more permeable blood-brain barrier and because they are often on multiple medications, meaning there could be a cumulative effect. Because of those risks, Narula said that patients with dementia should not be on these medications at all.

Past studies have shown that when patients go off anticholinergics the symptoms subside, but researchers are calling for a randomized control trial — considered the gold standard in research — so they can fully understand whether there is a real cause and effect link.

"At every [doctor] visit you should be going over all of your medications and saying, do I need to be on this? Is it working for me, and what are the risks and benefits and are there alternative agents that might be good for me and don't assume if it's over-the-counter that it's safe."

CBS News has reached out to the makers of the antidepressant, Paxil, for comment, but hasn't heard back.