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.
But when she reached 75, her memory began to fail. After tests revealed she had Alzheimer's disease, the siblings called a family conference.
"All of us kids came from wherever we lived and sat around the table," remembers Elaine. "We all knew there was something wrong with Mom, but to have it confirmed is awful. On the ride back I was with one of my sisters who also live in the Twin Cities and we cried. There is nothing you can really do."
"Mom just sat in the meeting, kind of like it wasn't about her," said Elaine. "She never really remembered getting the diagnosis."
Her family meant everything to her, but eventually, Margaret Albus didn't even remember who her children were.
"Once in a while she would say, 'Elaine,' and I would look at her. Wow, where did that come from?" said Elaine. "Sometimes she would know you and sometimes she wouldn't. It's really hard to see your parents -- someone to talk to about what's going on in your life -- and then they're not there anymore."
The Albus children know that one day this may be their fate. Some of them have already bought long-term care insurance and they talk about looking into nursing homes and assisted care facilities after reaching retirement.
"I kind of feel like it's for sure, out of seven of us, a couple of us are going to get it," said Elaine. "So you have to keep telling yourself it could be you, and be prepared for it."
But they say they keep their sense of humor.
"In my family it's become a natural thing to do," she said. "Every time someone forgets, we say, 'It's starting already.' We say we will get rooms next to each other. It's a little bit of denial, joking with each other."
"I fully expect that I will be in a facility," said Elaine, who is single and doesn't have children. "I want my nieces and nephews to get me in early enough. My one big fear is being one of those cat ladies, and the social services come in, and I am living in garbage with animals all over the place."
The Albus family had both the money and manpower to look after their mother, so care giving was not as stressful as it is for some families.
At first, Roger Albus looked after his wife, but soon, the siblings set up a weekend schedule to help give their father some relief.
"Six years ago, Dad was totally stressed out," said Elaine.
Kathy Cronick, 48 and the youngest, lives in Lady Smith. She checked in on her parents each day, handling the shopping and doctors' visits.
The others, who lived across Minnesota and Wisconsin, two or three hours away, set up a rotation, staying with their parents on weekends.
"I cannot imagine how a smaller family does it with not so many people to pitch in," she said. "It would be much more stressful."
Cronick said Alzheimer's disease is "always in the back of my mind.
"But there's nothing you can do about it and there are no cures, so what happens, happens. I just hope I forget quickly," she said. "I know it was really scary to see my Mom, but I don't dwell on it."
The siblings said they were lucky because their mother was "an easy person and always good natured," which is not always the case with Alzheimer's patients.