Finding a way to prevent Alzheimer's disease

More than five million Americans are living with it and every 70 seconds, a new case is diagnosed. Now with no cure in sight, researchers are trying a preemptive strike against Alzheimer's. CNN's Dr. Sanjay Gupta, a CBS News contributor reports:

Barbara and Jim Grdina have a half-century of memories together. They're both 75. Married for 53 years, together through high school, a honeymoon, five children. But now...

"What do I forget Jim?" asked Barbara

"A number of little things," answered Jim

Truth is, it's big things. Barbara has Alzheimer's. Jim, too has memory loss. Her mother and his mother died of the disease.

Alzheimer's Prevention Initiative

Daughter Kris, she worries about their future - and her own, with her 9-year-old son Andrew.

"It's very hard," said Kris, to watch what her mother and grandparents have been through. "It's very hard having known that and to look and see that that could be my course as well."

Knowing she's at high risk, Kris signed up for a clinical trial in Phoenix that will test a whole new approach to fighting Alzheimer's. In the U.S., researchers are looking for 50,000 people to participate.

"We need to intervene before the onset of memory and thinking problems to see if we can not only reduce the risk of Alzheimer's disease, but maybe - just maybe - completely prevent it," said Eric Reiman, executive director of Banner Alzheimer's Institute.

Dr. Eric Reiman is launching a second trial 3,000 miles away in Medellin, Colombia. Why here? It's home to the world's largest concentration of families with a rare gene defect causing Alzheimer's. People develop it early, in their 40s -- like Ricardo. He was diagnosed at 49. Hard to believe, this once loving father now abusive, and humiliates his sons.

"He does that because of the disease," said Ricardo's son Gabriel through a translator. "I love my daughter so much, and I wouldn't want to treat her like that -- without knowing I'm treating her like that -- like my father.

And so Gabriel and others at high risk will be taking experimental drugs and vaccines, before they suffer the same fate.

How will patients know if it's working if they didn't have symptoms in the first place?

"We'd be comparing people with and without the active treatment, to see if the fate of the brain has been affected by the therapy," said Dr. Pierre Tariot of the Banner Alzheimer Institute.

Doctors will rely on tests like brain scans to see if a signature of the disease - Amyloid plaque- is building years before memories are lost.

The dilemma for Kris now: whether to take unproven therapies-that may cause something as serious as brain swelling.

Kris says she would take the medication anyway even if it potentially has side effects.

"Yes," said Kris. "It's very sad to watch someone you love be in that position. I wouldn't want my son Andrew to have to do that. Alzheimer's is a very sad disease."

Researchers are right now deciding on which drugs to give people in the prevention trials.

Each drug gets two years to see if it works. If not, they'll move on to the next drug to see if it can slow down the brain pathology researchers believe is responsible for memory loss.