My mom has dementia. is there anyway to determine what stage shes in and when it most likely started?

Determining the stage of dementia and when it started can be done through clinical assessments, imaging tests, functional assessments, and caregiver reports. A comprehensive evaluation that combines these methods is necessary for an accurate diagnosis and to track the progression of the disease. Note that there is no single test or assessment that can definitively diagnose dementia.

Yes, we can determine whether she is mild, moderate, or severe by either office clinical testing or formal neuropsychological testing. A simple approach is the MMSE, and a more accurate approach is the MOCA. It is impossible to look backward and determine when this started, as most cases of dementia, like Alzheimer's, have initial changes years prior to clearcut clinical signs.