@bjordan2 The speaker was disingenuous, because true dementia is irreversible, even though its progress can SOMETIMES be slowed.

However, there are a number of medical conditions that can cause dementia-like symptoms. If these underlying causes are treated in a timely manner, the symptoms can be reversed. Here is a list of some of these:
https://www.healthline.com/health/dementia/reversible-dementia
This is why it is so important to get a competent evaluation when memory loss and other symptoms appear. We have a friend who has a condition called normal pressure hydrocephalus. Sadly, his wife was in denial that there was a problem, he was not treated in a timely manner, and now his condition is considered irreversible.