senile
adjective uk/ˈsiː.naɪl/ us/ˈsen.aɪl/
老朽的;老态龙钟的;（尤指）老糊涂的
showing poor mental ability because of old age, especially being unable to think clearly and make decisions
He spent many years caring for his senile mother. 他花了好多年照顾老态龙钟的母亲。
I'm always losing my keys these days. I think I must be going senile. 这些天我老是丢钥匙，我想我一定是老糊涂了。
Compare: doddery