Not sure if this article is the study you're referencing:
http://www.sciencedaily.com/releases...0126124721.htm
If so it said that anticholinergic medications, including Benadryl & other diphenhydramine drugs, were linked with developing dementia BUT it also says that second-generation antihistamine like loratadine (Claritin) for allergies are safe. Maybe Claritin would help instead?