Marty Reiswig's family has history of a rare, inherited form of early-onset Alzheimer's disease. The 36-year-old could undergo tests to learn if he will also get the disease, but he has chosen not to.
"Becoming closer and closer to the age of onset is kind of like a huge storm on the horizon," he told CBS News. "And some days I want to know if that storm is real and is going to hit me, and other days I'm terrified to know."
An estimated 5 million Americans suffer from Alzheimer's disease and that number is expected to more than double by 2050 as the population ages.
While the causes of Alzheimer's disease are not well understood, scientists have identified several rare genes that cause an inherited form of Alzheimer's in some families. This so-called familial Alzheimer's is rare, accounting for just 1 percent of all Alzheimer's cases.
Experts say if a person has inherited one of the genes, it is almost inevitable he will eventually get the disease.
"If you have one of these genetic misspellings you will develop Alzheimer's disease approximately 99.9 percent of the time," said Heather Snyder, Director of Medical and Scientific Operations at the Alzheimer's Association.
Reiswig's grandfather had this form of Alzheimer's, and his father started suffering from the memory-robbing disease in his early 50s. Now he's cared for by his wife Bonnie. "He has to be fed. He hasn't been able to speak since last June," she said.
Marty Reiswig is currently taking part in a National Institutes of Health-funded research project called the Dominantly Inherited Alzheimer Network Study. The study recently showed that brain scans can pick up changes 20 years before the first symptoms appear.
According to the NIH's website, the trial is testing two experimental drugs to assess their safety and efficacy in people who have a history of the genetic mutation that causes familial Alzheimer's disease. Scientists say the results of the trial will have implications for future studies and treatments for other forms of Alzheimer's as well.
"Our genetic problem might be the solution for so many other people," Reiswig said. "And might actually help cure Alzheimer's."