What are the narrations (hadiths) reported concerning olive oil, and is there a hadith that links its non-use to the onset of dementia?

It has been authentically reported in the prophetic tradition that the Messenger of Allah, peace and blessings be upon him, said: "Eat olive oil and anoint yourselves with it, for it comes from a blessed tree." Al-Albani graded this hadith (definition) as authentic. There are other hadiths whose authenticity has not been established, such as those related to olives and the use of theak (tooth-stick) or its use in treating hemorrhoids. Al-Albani ruled some of these as fabricated or weak. There is no hadith that links dementia to not consuming olive oil.