They've analyzed data of 500 people, age 70 to 75, who have normal brains. Results show that peoples who took at least one anticholinergic medication performed poorer in the short memory test compared to those who did not take over-the-counter cold medicine.
You and I have heard that list of side effects -- dry mouth, blurred vision, constipation, drowsiness, hallucinations, difficulty urinating, confusion, delirium, etc. They never say "any medicine can cause these symptoms," they just REPEAT IT!!!
Yii -- I've used them -- all of the antihistamines named above, so now my shrunken brain is planning what to do tonight about getting to sleep tonight without taking any of those pills.