Alzheimer’s disease (AD) is the prodromal stage of Dementia. Imagine the disease as a continuum, beginning with Mild Cognitive Impairment (MCI) to possible/probable AD, and ultimately Dementia, the end-stage. Not all healthy people will have MCI, and not all MCI will result in AD. However, there is research evidence that a substantial proportion of people with AD-type MCI will progress to AD and subsequently Dementia. On the other hand, several findings suggest a possible reversal of AD-type MCI with carefully administered behavioral therapy, including brain-stimulating exercises. In addition to a good diet (the Mediterranean diet preferred), a minimum of 30 minutes of daily exercise, social connectedness (community groups, family, friends), and brain-stimulating exercises have been associated with possible reversal or delay of AD-type Dementia.
The figure below gives a clear overview of the Alzheimer’s disease Dementia continuum.

Below, I provide a list of websites where you can try out different brain-stimulating exercises:
BRAINGLE: Braingle is a place to solve puzzles, brush up on your trivia, play games and give your brain a workout.
brainHQ: American Association of Retired Persons (AARP) brain training exercise.
JigZone: Online Jigsaw Puzzles
Lumosity: Personalized brain training.
WholisticResearch: Brain exercises to improve cognitive performance and memory retention.
For additional information on Alzheimer’s disease and Dementia, visit https://www.alz.org/.
There is hope, even when your brain tells you there isn’t.
John Green