Doctors have used the term senile dementia for decades. Senile means old. But when was dementia first discovered?Scientist and doctor Alois Alzheimer presented a paper on what we now call Alzheimer's Disease in 1906. It was the first paper describing a clinical case of dementia and was an examination of the behavior of Frau Auguste D.so he was was credited with dementia discovery. So when was dementia first discovered would be officially in 1906.