Some years ago dentists figured out a correlation between chronic gum disease and Alzheimer’s. Typically bacteria are filtered out by the blood-brain barrier, but there is a direct vascular route from the gums to the brain.
So the dentists figured out that the five types of spirochete bacteria were traveling to the brain, dying, and leaving plaque behind as their remains.
But the solution to this was simple: brush with powdered baking soda, which kills those bacteria in just five seconds; alternating every other day with an ordinary fluoride toothpaste.
Back when baking soda was a common tooth powder, Alzheimer’s was rare. When there was the great shift to toothpaste, plus a few decades, was when Alzheimer’s really took off.
It may have to do with skyrocketing ages in the 21st century.
I'm not sure it was rare but rather called "senility"......