SENILE

[adjective] - showing a lack of mental ability because of old age, esp. a lack of ability to think clearly and make decisionsHe spent many years caring for his senile mother.He was too senile to stand trial as a war criminal.I'm always losing my keys these days. I think I must be going senile.Alzheimer's disease is the commonest form of senile dementia (= the medical condition of being senile).