During the 11 years that Margaret Albus lived with Alzheimer's disease, the worst moment came in the middle of one night, when she called out to her daughter, panic-stricken: "I just want to know who I am."
"I am almost crying now," said Becky Albus, a 53-year-old optician who was looking after her elderly parents that weekend. "I would have done anything not to let her be scared."
Margaret Albus died on Dec. 31, 2009, at the age of 86. But she had mentally slipped away a decade before. She had seven children.
"It's the disease of the long goodbye. It's a perfect description," said another daughter, Elaine Albus, 51, a team leader for a Minnesota business improvement company.
"The fear in her eyes, it's hard to watch over and over again," she said. "There's nothing you can do about the terror but say, 'Mom, it's all right. We'll take care of you.'"
All seven of Margaret's middle-aged children -- four sisters and three brothers -- are at increased risk for developing Alzheimer's disease.
A decade ago, they volunteered to be part of a study at the University of Wisconsin to find genetic markers for the disease that today affects 5 million Americans.
The goal of the study, the largest of its kind, is to identify people in middle age and follow them in the hopes of learning how the disease develops.
Scientists hope that if they can find markers to predict eventual onset, they can develop early interventions.
"This is a terrible disease and to have a parent or anyone in the family [with Alzheimer's] leaves an indelible mark," he said. "The loss of identity and loss of personality -- we have an organ called the brain that is who we are."
The disease affects so many people that when the study was announced 10 years ago, the institute got 600 phone calls in the first 24 hours.
"We never had to recruit, that's how much interest there was in the study," he said. "And people have traveled large distances to be a part of it."
Now, the study includes 1,500 participants with a mean age of 53, including all seven of the Albus siblings. The hardest part has been finding those who don't have a family history -- and a compelling reason to participate -- for a comparison group, according to Sager.
Risk factors for the disease include increasing age and abnormalities in the apolipoprotein E gene (APOE), which is on chromosome 19 and has three different alleles, or alternative purposed, like those for eye and hair color.
One -- the e4 allele -- is associated with increased risk. Not all who have this gene will go on to get the disease, but they are more susceptible.
APOE was first recognized for its importance in lipoprotein metabolism and cardiovascular disease, but has more recently been studied for its role in the onset of Alzheimer's disease.
About 44 percent of the study participants have APOE abnormalities. They have more than double the risk of the general population, 15 to 20 percent of whom have that gene sequencing.
"The disease is more prevalent in women because they live longer," said Sager.
Disease onset is typically in the late 70s and early 80s. By age 85, 30 to 50 percent of adults have symptoms.
Margaret Albus, a homemaker, raised her large family in the small Wisconsin town of Lady Smith, where her husband Roger ran a business that made conveyers for farm equipment.