Hello,
My name is Jan Smisek, and I work as clinical psychologist in Czech Republic. While studying english written texts about dementia, i repeatedly find terms "incident dementia" and "prevalent dementia".
For example: "...free recall outperformed total recall in identifying incident and prevalent dementia in this primary care cohort..." and many others.

Could you please explain me what "incident" dementia and "prevalent" dementia means? Google was no use in this case.

Thank you a lot.