My Wife Has Been Treated For Chronic Cough For Roughly

My wife has been treated for chronic cough for roughly one year.. She has dementia and is on Donepezil 10mg and Cymbalta 60mg. X rays, CT scan, Sinus scope with Ear, Nose and Throat specialist. She has had a stress test to check her heart condition and everything normal.A lung capacity test at hospital. Has tried an inhaler, two different antibiotics at different times, cough medicine under prescription.Has had an Bronchology most recently and that is negative. Gabapentin , low dose, has been suggested to deal with the pain by the radiologist. Could medicine be the cause or dementia is playing a role? I would have to say her memory has noticeably declined slowly for the past 4 years. Appreciate you input.
Bill