The shadow of Alzheimer's hangs over the Sturmer sisters.
Their father died of the disease, and their grandmother before him. Both paternal uncles their father's twin and an older sibling have struggled against its relentless progression.
Does Alzheimer's live within the sisters as well? Have the tangles and plaques that would rob them of memory begun to take shape in their brains?
All that the sisters, Debbie Sturmer Long and Tami Sturmer DeLauro, know with certainty is that they're at risk, and they're worried.
These two women one on the West Coast, one on the East grapple with questions of genetics that could shape the future, for them, their children and grandchildren. Could science help their family? Could they help science?
Debbie wants answers where there may be none.
With a troubling family history of Alzheimer's including early onset of the illness in her father, who was diagnosed in his early 60s she wants to know if she carries a gene that researchers say can indicate an increased lifetime risk of developing the degenerative brain disease.
"I think I want to get tested," said Debbie, 55, who lives in Sacramento and works for the state. "I've always been a pragmatic person. I'd want to get all areas of my life locked down before you can't do any more."
Back on Long Island, where they were raised, her sister doesn't really want to think about it. Tami is 53 and a geriatric care manager. She sees the devastation that Alzheimer's wreaks on her patients and their families, and she watched her father's decline and death.
If that's what she is facing, she'd rather not know.
"You want the honest truth?" Tami said. "Everything bad that's in our genetic heritage, I seem to have gotten. The odds are stacked against us.
"If I knew ahead of time that I would get Alzheimer's? I don't even want to give that answer. I don't want to put my kids through that."
For so many families living with Alzheimer's, answers seem tantalizingly close yet maddeningly far.
The disease affects 5.4 million Americans, or one in every eight older adults. It is the nation's sixth-leading cause of death.
Scientists can describe the abnormal progression that marks the disease: a toxic buildup of beta amyloid protein that prompts the formation of tangles and plaques that kill brain nerves and block communication between neurons. They can describe the symptoms: emotional outbursts and behavioral changes as the outer layer of the brain begins to shrink; a gradual loss of memory and self; and ultimately, loss of life.
But they don't yet understand what causes the buildup of protein clumps. They can offer no preventive measures or cures.
Based on current research, scientists believe only a tiny fraction of Alzheimer's cases less than 1 percent worldwide are a direct result of genetics: specifically, a rare and inherited genetic mutation that causes the disease to take hold in the 40s and 50s.
"It's a deterministic gene," said Jessica Langbaum, associate director of the Banner Alzheimer's Institute in Arizona. "You will certainly develop Alzheimer's if you have it."
Researchers know of only 300 families around the globe that carry this rare genetic mutation.
But millions of people and as many as 20 percent of Americans may carry another gene called ApoE4 that has been found to increase the risk of developing Alzheimer's disease as they age.
Apolipoprotein E is a protein that helps distribute cholesterol throughout the body. Researchers have found that its fourth genetic alternate, ApoE4, is associated with susceptibility to a range of brain problems, such as cognitive decline, faster progression of multiple sclerosis and Alzheimer's disease.
"If you happen to carry ApoE4, your risk of developing Alzheimer's is greater, but there are many cases of people who carry the gene and don't develop the disease," said Langbaum.
"And there are plenty of people who don't have the gene who do develop Alzheimer's."
Disease traced to grandmother
The Sturmers' history of Alzheimer's disease begins with their grandmother, Betty, the daughter of immigrants who settled in New York after 1900.
"She's the first one we know of who had Alzheimer's," said Debbie, "and she was adopted."
Her husband, Harold Sturmer, was an accountant in Queens. Betty raised their three sons the oldest born in 1931, and identical twins born in 1934.
By the time she was in her 70s, Betty and Harold had moved to Florida. So had one of the twins, Stanley David Sturmer, the father of daughters named Debbie and Tami.
Betty Sturmer died of Alzheimer's at age 78 in 1987.
"My father was really hit hard seeing his mother go through Alzheimer's," said Debbie, "so when it came to his own illness, he didn't want to talk about it. Which makes it harder for everyone who follows."
He liked people to call him David. By the time Debbie was 5, her parents were divorced. For years, he worked as a barber in New York, then in Florida, where he opened a shop called Dave's Place in Delray Beach and sang opera to his customers.
A decade after his mother's death, Stanley David Sturmer developed Alzheimer's. Years later, so did his twin and their older brother, who are both still alive.
"Three brothers, that whole generation, got Alzheimer's," said Tami.
Her father and stepmother used to spend holidays and summers in New York with her. Even before David told them he was diagnosed, Tami began noticing that he would get confused. Normally talkative, he would forget words and grow taciturn.
"For a while, I thought, 'Maybe my dad's playing with me,' " she said. "Everybody else said he seemed OK. I have a history as a geriatric care manager, but I stepped into the child's role. I had blinders on for a while."
Eventually, both sisters noticed their father's stilted speech, forgetfulness and changed personality.
"The last time we saw him, he didn't know who we were any more," said Debbie. "He was at his day care program, and he introduced my husband, my sister and myself as his wives."
Their father was 74 when he died in 2008.
"When I was young, he was the fun grandpa," said Debbie's daughter, Robin Deller, who is 34 and pregnant with her second child.
"One of my mother's biggest concerns, I didn't realize until recently, is just spending time with her grandkids.
"She's worried she won't have enough time with them before the possible onset of Alzheimer's."
Onset isn't preordained
There is much that Alzheimer's researchers don't yet understand about the disease, but they do know this much: Biology is not destiny.
A significant family history increases risk, certainly. So does carrying the ApoE4 gene. But neither guarantees a future haunted by Alzheimer's.
"If someone has a family history of Alzheimer's, every time you have a middle-age pause or senior moment, you think it's happening to you," said Gary Small, director of UCLA's Memory and Aging Research Center and the author of several books on the disease.
"But for the average person, genetics counts for about one-third of brain health as they age."
Even so, for a person with a first-degree relative a parent or sibling, for example who was diagnosed with Alzheimer's, the risk of developing the disease doubles, a fact that researchers say sounds more dramatic than it is.
For the Sturmer sisters, said Charles DeCarli, director of the UC Davis Medical Center Alzheimer's Disease Center, "They have a strong family history. They're worried.
"But in families like this, the established likelihood is twice as great over their lifetime. They probably have a one out of 10,000 chance of getting dementia now. That's hardly a risk to worry about right now."
The greatest predictor of Alzheimer's is age: Only 5 percent of people at 65 or 70 have the disease, according to the Centers for Disease Control and Prevention, but almost half of people 85 and older will develop it.
Studies show that twins even identical twins don't necessarily share the same fate with Alzheimer's. Even when they both get the disease, said DeCarli, the onset for 60 percent of twins is more than five years apart.
The reasons for that can vary. Did one twin suffer a head injury earlier in life? Was there untreated depression or other illness, or perhaps alcohol or drug abuse? Even birth order could play a part, said DeCarli.
And experts know that lifestyle is a factor in maintaining health in the aging brain and can possibly delay Alzheimer's disease.
"That can empower people," said Small. "Physical exercise, diet, nutrition, stress management and mental stimulation can protect the brain. Even with genetic risk, lifestyle can make a difference.
"People have more control than they think over their brain health."
Researchers differ on tests
Although research has shown that people who have been tested for the ApoE4 gene tend to handle the results without much anxiety, neither Small nor DeCarli recommends widespread testing for the simple reason that carrying the ApoE4 gene does not predict who will get Alzheimer's.
As DeCarli said: "Unless someone has a diagnosis, why would I do genetic testing? There's no evidence that testing for ApoE4 will help. It only indicates a lifetime risk factor for getting dementia."
If families such as the Sturmers are concerned, the Alzheimer's Association recommends that they consider a base line evaluation, including family and medical history, brain scans, cognitive testing and lab work, to assess brain health.
"Frequently, diagnostic centers come back and say, 'Your memory is in the normal range,' " said Judy Filippoff, an Alzheimer's Association of Northern California program coordinator. "But you've at least established a relationship with a diagnostic team."
On the other hand, Langbaum, at the Banner Institute, suggests both genetic testing and participation in research.
"We're in a new era of Alzheimer's disease preventive research," she said. "I think in coming years, there will be something new.
"If people find out their ApoE4 information now, they can make the decision to enroll in a preventive trial or at least explore a healthy lifestyle centered on diet and exercise."
The scientists don't agree, and neither do the sisters.
Debbie Long wants to know if she carries the ApoE4 gene. She started an exercise program to manage some of the lifestyle factors, and she signed up for the Alzheimer's Prevention Initiative, an online registry to match people with clinical research.
"As I get closer to retirement, I want to get more involved," she said. "I definitely want to be tested."
Tami DeLauro doesn't see the need. Alzheimer's has struck her family too often for her not to be worried, but she thinks helping medical science unravel the mysteries of the disease would be overwhelming for her.
"There are no treatments," she said. "Everybody's optimistic about the research, and that raises hope. But until there's really something out there to prevent or cure this, it's too scary.
"I don't think I could live with myself knowing the outcome of testing. If Debbie can do that, more power to her."
Two sisters, two different approaches because for all the reassurance that statistics can provide, scientists can't yet promise a cure for their family's cruel history.
Call The Bee's Anita Creamer, (916) 321-1136.