It is the sixth leading cause of death in the United States, and for families dealing with Alzheimer's it can seem hopeless.
But this story might change your mind.
Who can tell you about the benefits of laughter? Ken and Barbara Johnson....
"We could sit and cry about it or we could try and make the best of it and laugh about it as much as we can," Barbara said.
It started in 2011 when Ken couldn't remember his grandson's name. It wasn't long before doctors diagnosed ken with mild cognitive impairment.
"I failed miserably," Ken said. "Just simple words, one-syllable words I couldn't remember."
Mild cognitive impairment affects Ken's memory and judgment and puts him at a higher risk for Alzheimer's- the most common form of dementia.
"It's not just a memory, a short-term memory loss," he said. "It's a definite personality change, and not for the better."
Building model boats is one of the hobbies that Ken is determined to hang onto, keeping your mind and body active is critical.
Dr. Henry Paulson, the director of the Michigan Alzheimer's Disease Center, is optimistic about new evidence showing exercise can protect your brain.
"Use it or lose it," he said. "If you don't use parts of your body they start to shrink. We advocate that everyone come up with some sort of exercise."
Ken and Barb eventually found support at the Alzheimer's Association and they share their story, hoping for a cure, preparing for the worst.
"I think it’s the loneliest disease in the world," Barb said. "You can be right there with that person, and the thing you are most afraid of is that the day will come when they don't recognize you."
For more information on how you can get involved with the Alzheimer's Association and the resources available, go to alz.org