I don't buy this in general because of my personal experience. I knew someone who took lithium for manic depression for many years. It certainly did not prevent dementia in his case. (That is putting it mildly.) He had been an extremely intelligent person.
Then it is all settled. You know one person with a mental illness that lithium did not stop memory loss so all the studies and research are wrong.
BiPolar is a mental illness. Dosages of 300 to 600 MG a day of lithium. Usually other drugs are taken that can take away short term memory. Some have schizo affective disorder with bipolar and neurontin and other powerful drugs are taken for psychosis.
I am not talking about a mental illness. I am talking about strengthening the brain so dementia or stroke does no further damage. 5 to 15 mg of a OTC supplement of lithium. Lithium is found in tomatoes. But no many want to eat 100 tomatoes a day to get what a person needs.
I am not here to convince you. It is up to each one to do their own research.