Donald Trump scored a full 30 out of 30 on the Montreal Cognitive Assessment (MoCA), which is used by medical professionals to test for dementia.
The 10-minute test was created in 1996, and assesses concentration, attention, memory, language and other skills.
Here is a snippet:
You can see the full test pdf here (only for educational purposes, commercial purposes please see MOCA site above)
(Adding one point if the subject has fewer than 12 years of formal education.
Around 16: cognitive health of an Alzheimer's patient
Around 22: cognitive health of someone with Mild Cognitive Impairment (MCI)
Above 26: Normal 30: Perfect score (Trump scored 30/30)