Not with regard to the acute mental decline of Alz or dementia, which seemingly are a lot of trauma for many involved, but perhaps there is some adaptive function to slight memory loss with aging? Maybe old people don't want to remember everything? Idk.

If reincarnation is real, that involves a total memory loss at the terminal age limit, so that is somehow adaptive, allowing a new growth of life. Maybe slight memory loss in the aged allows a refresh or new growth of life. A sort of lightening of the burden, perhaps? To let the aged evolve into a new phase of life? Letting go of the past?

There could be something to that. The wisdom of the elderly may be related to an ability of such pruning to permit sight of the forest for the trees, the gaining of perspective.