Jamie Tyrone, right, does stretching exercises during a fitness class at the Clayton MD Total Health Center in San Diego, Calif. (Sandy Huffaker/The Washington Post)

When Jamie Tyrone found out that she carries a gene that gives her a 91 percent chance of developing Alzheimer’s disease beginning around age 65, she sank into a depression so deep that at times she wanted to end her life.

Then she decided to fight back. She exercised. She changed her diet. She began taking nutritional supplements, including fish oil, vitamin D, vitamin B12, curcumin, turmeric and an antioxidant called CoQ10. She started meditating and working mind-bending puzzles, such as Brain HQ. She joined a health clinic whose regimen is shaped by a UCLA medical study on lifestyle changes that can reverse memory loss in people with symptoms of dementia. She started a nonprofit group, Beating Alzheimer’s By Embracing Science (BABES), to raise money and awareness about dementia.

“I found my voice,” said Tyrone, 54, a registered nurse who lives in San Diego.

Perhaps the only thing as bad as Alzheimer’s disease is the fear among a growing number of older Americans that they may be at risk of the neurodegenerative disorder, which robs memory and cognitive ability and is the leading cause of dementia.

Jamie Tyrone, right, does push-ups with other classmates during a fitness class at the Clayton MD Total Health Center in San Diego, Calif. (Sandy Huffaker/The Washington Post)

A 2011 survey for the MetLife Foundation found that the only disease more dreaded than Alzheimer’s was cancer. A Harris Poll conducted in April for Aegis Living, an assisted-living and Alzheimer’s care company, found that the worries cross all generations: more than 75 percent of millennials, Generation Xers and baby boomers worry about what will happen to their memory as they age.

Some, like Tyrone, fear Alzheimer’s because genetic testing shows that their risks are higher than for others. Many more fear Alzheimer’s because they saw what the incurable disease can do. They saw a parent, a grandparent or other beloved relative slip away in the twilight of their lives through the steady erosion of memory, cognition and identity as the disease progressed. Now they worry whenever they misplace something or forget a name, and vow that they will do whatever they can to prevent or delay its onset.

“It’s my nightmare: the loss of my mind; the inability to recognize people who are dear to me; the ability to think,” said Charles Goldman, 71, a semi-retired attorney who lives in Silver Spring, Md. Goldman, whose mother had Alzheimer’s, said he is vigilant for possible lapses in his own memory, but he also does everything he can to lower his risk of developing dementia. He works out at a Montgomery County recreation center. He reads like crazy, both fiction and nonfiction. He follows the news about possible new treatments or research studies. He does the crossword puzzles of every Sunday paper he can get his hands on. He gobbles almonds.

“I can accept the idea I won’t be able to run 10K races. I can’t accept not being able to understand what people are saying or recognize people.”

Joanne Omang, a former Washington Post correspondent, also watched her mother die of Alzheimer’s and saw how dementia transformed her and others.

“People become like children in many ways. They steal food. They fight having baths. They become violent in many ways,” she said.

It’s different than death, and in some ways worse, the way her own mother seemed to disappear before her eyes, Omang said.

Chuck Goldman, who believes he is at risk to develop Alzheimer’s disease, adds a weight to his ankles as he participates in a fitness class for seniors in Burtonsville, Md. (Bill O'Leary/The Washington Post)

Like others, that was enough to spur her into action. Omang doesn’t consider herself a worrier, but “when I simply cannot remember the name of someone or something, when I know that I know it, I do ask myself, ‘Is this a sign?’ ” she said in an e-mail. “I’m keeping count.”

So Omang eats blueberries every day, having seen studies suggesting that the fruit is beneficial for brain health. She hits the gym almost every day for strength and aerobic workouts. She does word puzzles and keeps up the Spanish skills she honed in Latin Americaas a foreign correspondent. And she said that if she should develop dementia, she will move to a state that permits euthanasia so that she can die in peace.

“I don’t want to be a burden to anybody like that,” Omang said. “There’s nothing worse than this disease.”

Understanding the risks

More than 5 million people are living with Alzheimer’s, and as the population’s median age rises, the number of cases is expected to increase to 13.5 million by 2050, according to the Alzheimer’s Association.

“The bad news is we think Alzheimer’s affects half of everyone over 85. So we’re all in this together,” said Eric M. Reiman, executive director of the Banner Alzheimer’s Institute in Phoenix.

But the risks can also be overstated, especially for early-onset forms of dementia. Unless one has a genetic predisposition, Alzheimer’s strikes the majority of people after they reach the age of 65, according to the Alzheimer’s Association. A history of high blood pressure, diabetes, smoking, obesity or cardiovascular problems increases one’s risks of developing dementia.

But aging itself is the biggest risk factor: The longer you live, the more likely you are to develop Alzheimer’s or another form of dementia.

Dallas Anderson, program administrator for population studies for Alzheimer’s and dementia at the National Institute on Aging, said a healthy, 65-year-old woman has about a 17 percent chance of developing Alzheimer’s. It’s 9 percent for men, partly because their expected life spans are shorter, Anderson said.

Heightened risks for Alzheimer’s also come from carrying certain genes.

The most clearly documented risk comes from having DNA for apolipoprotein E-e4, a variation of a gene that codes molecules to transport cholesterol through the bloodstream. This gene raises one’s risk of late-onset Alzheimer’s by 10 percent for people older than 65, and by 50 percent for those over 85. Having two of these genes — one from each parent — as happened with Tyrone, increases the risks even more, though even then it is by no means certain that the person will develop dementia.

Early-onset Alzheimer’s can strike between 30 and 60 years old, but it’s also the rarest form of the disease. Only about 5 percent of all Alzheimer’s cases involve early-onset. Most of those are caused by a mutated gene inherited from a parent that affects chromosomes 21, 14 and 1, each of which can cause abnormal proteins to form. The odds of inheriting the gene from a parent are 50-50. If the person does inherit the genetic mutation for familial Alzheimer’s disease, he or she will almost certainly develop dementia at the same age as the parent who developed the disease.

But as scientists shed more light on possible causes and risks, a number of studies have pointed to possible, if not fully proven, measures that may at least postpone the appearance of symptoms.

“We have data from epidemiological studies and some biological studies that suggest, but do not prove, that certain factors might reduce the risk of Alzheimer’s disease,” Reiman said.

One such study was performed at the UCLA Mary S. Easton Center for Alzheimer’s Disease Research and the Buck Institute for Research on Aging. The study, written by Dale E. Bredesen and published last year in the online journal Aging, found that a 36-point therapeutic program reversed symptoms of memory loss among participants.

Their carefully prescribed regimen included dietary changes, vitamin supplements, stimulation with online brain teasers, physical exercise, optimized sleep and some medications. The researchers acknowledged that their study sample was small but also suggested that the results were worthy of further explanation.

But Anderson said people need to be realistic.

“Whatever steps they take — whether it’s diet or exercise or staying socially engaged or cognitively active — those steps will not guarantee that the individual will be spared,” Anderson said. “I think the best that we can hope for right now is to postpone the condition. It’s not preventing — it’s postponing. And that’s not shabby. If somebody can get an extra five years of independent living, that’s big.”

After all, he said, a lot of the possible strategies for reducing Alzheimer’s risk are not unlike chicken soup: “They may not help. But they couldn’t hurt.”

‘I went into a dark hole’

Tyrone found out about her genetic disposition for Alzheimer’s by accident. She submitted to genetic testing after noticing problems with her balance and worrying she might have multiple sclerosis. Instead, she discovered that she had near-certain odds of developing Alzheimer’s because she had inherited an ApoE4 gene from each parent.

It suddenly made sense, because Alzheimer’s had struck Tyrone’s family several times. On her mother’s side, her great-grandmother, grandmother and two great uncles had suffered from dementia; so did her father, whose Alzheimer’s diagnosis was confirmed by autopsy.

“Emotionally, I went into a dark hole. I’m frightened, I’m scared, I’m alone, I’m isolated,” she recalled feeling at the time. She couldn’t disclose the results beyond her immediate family for fear that she would be discriminated against by employers or by insurance companies. Religious beliefs prevented her from taking her own life, she said.

Then she overhauled her life, including her diet and habits. She went on the Paleo diet— which is modeled after what prehistoric humans are thought to have been eating — and began working with David Clayton, a physician whose Total Health Center in San Diego helps people supervise a regimen of diet, intense exercise and brain stimulation. She became a self-described “lab rat.” She enrolled five years ago in a study at the Banner Institute that requires two full days of testing in Phoenix, including brain scans and cognitive and memory tests, followed by checkups every two years. She has also agreed to donate her brain to science after she dies.

Tyrone said she believes her work could delay the onset of Alzheimer’s by a few years, but she hopes for at least another 10 healthy ones. Even if the regimen has not have given her complete peace of mind, she said, at least it has given her a renewed sense of purpose. “I’m not as fearful as I was before,” she said. “We may not find a cure in my generation, but I believe we will find a cure for the next generation.”