Do certain drugs cause dementia? Or are the authors misguided?

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Screen Shot 2015-02-02 at 2.36.39 PMA new paper published in JAMA Internal Medicine makes an interesting claim that a class of drugs called anticholinergics may cause dementia and Alzheimer s disease.

But, you shouldn't be too worried. The most that can be concluded from a study conducted at the University of Washington in Seattle is that there is a correlation and a weak one at that between the use of a wide variety of drugs and the development of senile dementia and Alzheimer s Disease (AD) years later.

Lead author Shelly Gray, PharmD acknowledges some of the limitations of the study: "It isn't possible to prove causation with observational data. I would say that we haven't proven that these drugs cause dementia, but our results certainly reinforce concerns about this issue."

Maybe, or maybe not. Perhaps more puzzling is the lack of biological plausibility. Gray says, Future studies would focus on understanding the biochemical mechanism that might underlie this association.

To which ACSH s Dr. Josh Bloom responds, They've got their work cut out for them. It is certainly plausible, if not likely, that the use of these drugs can affect short term cognitive ability because of their side effects. The last time I took a Benadryl, I woke up the seal pool in Central Park the next morning.

But, he adds, it is very far from clear how drugs like this, or any other drug, really, could promote the formation of beta-amyloid plaques the hallmark of AD in the brain. A number of mechanisms have been proposed for plaque formation, and research has focused on finding drugs to block it. Yet, there is still not one single disease-modifying drug for AD. This theory just seems too simple to be true.

And ACSH advisor and uber-statistician, Dr. Stan Young is not all impressed with the magnitude of the increased risk. He says, A risk ratio of less than 2.0 (double) after full freedom to do the analysis any way the authors like is very weak evidence at best and totally misleading at worst. In this study, the highest risk even in the people who took the most drugs was 1.5 (a 50 percent increase), so what they are seeing may simply be an artifact of poor data weak statistics.

An accompanying editorial by Noll L. Campbell, PharmD and colleagues of Purdue University fully supports the findings of the original paper, but goes a little too far: [T]his study provided the strongest evidence to date that anticholinergic drugs cause dementia.

Excuse me, says ACSH s Dr. Gil Ross. The editorialist makes two major errors here, either of which should lead to his being sent to an Epidemiology and Statistics 101 re-education camp: 1-the data here, as noted above, do not even warrant a suggested association, much less ¦.2-his allusion to a causal link to dementia. Not even close.