senility

noun3

1. •
   The bodily and mental deterioration associated with old age: Synonym of senescence.
2. •
   The losing of memory and reason due to senescence.

   • He was entering his years of senility and not liking it a bit.
3. •
   (no longer used) An elderly, senile person.

   • There was no need for George Playford to talk as if they were doddering senilities. — 1934