How long does it take for a doctor to notice or identify dementia?

my mother had several doctors none of whom diagnosed dementia even though i knew she had it. they just kept saying old age. no help whatsoever

To be fair even someone being treated for a chronic illness only sees their doc for a few minutes a month, they can't be expected to pick up the little changes of early dementia, especially if they are not alerted to be looking for it. It might help to document the changes you are noticing in your mom and to give the doctor a heads up. Even if you haven't got the authority in place to discuss your mother's heath care most doctors will take a family members input into consideration.

about 5 yrs ago I asked my mom's doc if there were some type of "baseline" cognitive screening, which would be re-checked every 5 yrs. this is a "BEST DOC" of our major metro area winner type doctor. He looked at me like **I** was the crazy one for even thinking to do such a test. Now, 5 yrs later, mom is obviously not the same person, getting not only frail but quite forgetful. If she had had a "baseline" cognitive test done 5 yrs ago, as **I** had suggested, we could be seeing, in a scientific way, her decline.
I truly wish I had INSISTED on cognitive testing.

my mums dr did cognitive testing and brain scans that showed loss of brain tissue which he said was normal old age. the other dr im sure thought my mum had mental health issues otherwise why wouldnt they even mention dementia? perhaps if theyd properly diagnosed it in the first instance she couldve had medication to help. im in australia so i dont even kniw if we have medication available? i think thats the problem they know there isnt anything to prescribe so they just dont do anything at all.

There are a few medications that can help, but not with every patient. Truth be told, my mom would get much better if she would have stayed more active. She had a gym membership in walking distance, never used it. Her diet also is not helpful in the least--too "white". Meaning white flour, white sugar, not enough fruit/veg, and too much ice cream, cookies, pie crust with not much filling....

The docs may or may not diagnose dementia but you're in a better position to tell if she is declining mentally. Read up on signs of dementia on this site. My father clearly has dementia, no short memory, lack of reasoning ability, even though he has always refused to be tested. In our case it's very clear with or without medical diagnoses.