presenile dementia

The same condition as senile dementia, however describes the condition when it occurs before the age of 65.

Idiot: I think the fact he is placing these objects in such places is due to the Alzheimer's causing senile dementia, we'll have to keep an eye out for Disorientation and Memory loss as well as changes in personality, thank god im chief lecturer at Harvard.
Me: You're a twat, its presenile dementia he is only 64.