THURSDAY, Aug. 25 (HealthDay News) -- Alzheimer's disease is one of the most dreaded afflictions of old age, but the announcement by celebrated women's basketball coach Pat Summit of her Alzheimer's diagnosis at age 59 has put a spotlight on the less common, but perhaps even more devastating, form of the disease.

About 500,000 people in the United States, or about 5 percent of those with Alzheimer's, have early-onset Alzheimer's, also called "young-onset" because it's diagnosed before age 65, said Dr. Zoe Arvanitakis, a neurologist in the Alzheimer's Disease Center at Rush University Medical Center in Chicago. Though rarer still, diagnoses among people in their 30s and 40s aren't unheard of, she noted.

"In contrast to what many people think, Alzheimer's disease does not only affect older persons. It can also affect persons in their middle adult ages," Arvanitakis said.

Symptoms for early-onset Alzheimer's are the same as for late-onset disease, experts said. Summit, coach of the University of Tennessee Lady Vols, told the Washington Post this week that she suspected her forgetfulness was a side effect of a rheumatoid arthritis drug, until Mayo Clinic doctors told her she was showing mild signs of the dementia.

Typically, early-onset Alzheimer's progresses more quickly than late-onset Alzheimer's, experts said.

Still, the time from which a person first has symptoms to the time they've lost so much of their mental abilities that they're truly disabled varies widely from person to person, said Dr. Gary Kennedy, director of the division of geriatric psychiatry at Montefiore Medical Center in New York City.

For older patients, that may be 10 to 15 years; for younger ones, time to disability is usually around five years, Kennedy said.

Younger patients also have a different set of worries than older patients. Many are still working, have mortgages and even families to support, Arvanitakis said.

Recently, a change in federal law enabled patients with early-onset Alzheimer's to receive Social Security disability insurance (SSDI) and supplemental security income (SSI) more easily, Arvanitakis said.

"There used to be significant roadblocks," she said. "I remember five, 10 years ago trying to help my patients get on disability being told, 'What proof do you have they have Alzheimer's disease?' It was hard for me to convince them it was true."

Because it's relatively uncommon, people in their 40s and 50s with Alzheimer's can have difficulty getting a diagnosis. Apathy and loss of interest in things once enjoyed can be one symptom of Alzheimer's. But that's sometimes mistaken for depression, Arvanitakis said.

Several gene mutations are believed to contribute to Alzheimer's in younger people, and early-onset Alzheimer's can run in families that have a hereditary component. But for other people, what causes Alzheimer's is unknown, experts said.

In addition to having a close family member such as a mother, father or sibling with early-onset Alzheimer's, having a major depressive episode as an adult also appears associated with going on to develop Alzheimer's, Kennedy said. Many people with Down syndrome also eventually develop the disease.

There are no medications that can slow or reverse the underlying biological processes that lead to damage in the brain. But like older people, younger people can benefit from certain drugs that boost levels of a neurotransmitter in the brain that is important for forming memories, Arvanitakis said.

Those who fare the best tend to be those who have a strong support system of family and friends, she said.

High blood pressure, stroke, diabetes, heart rhythm abnormalities and high cholesterol can reduce blood flow to the brain and lead to "vascular dementia," another form of progressive decline in memory and thinking skills, Kennedy said. Research has shown that many people with Alzheimer's also have vascular changes in the brain.

To combat that, "it makes good sense to follow a heart-healthy lifestyle," he said.

Those who are intelligent and educated also have brain "reserves" that they can use to cope with the brain degeneration and continue to function, at least for a time, Kennedy said.

"They have the software to compensate for what's happening to the hardware in the brain," Kennedy said.

And although the disease is relentless and people continue to lose memory and thinking abilities, there is often time before that happens to work, to accomplish things and to enjoy life, Arvanitakis added.

"If you're the type of person who is energetic and wants to fight it and do everything possible, we do have patients that live with this diagnosis for many years and continue to lead a fulfilling and productive life," she said.

Summitt is nothing if not determined. She's won more victories than any other college coach, men's or women's, and eight national titles. According to news reports, Summitt has said she does not believe her symptoms are severe enough for her to step down as coach, and that her goal is to coach at least three more years, if possible.

She also told her team about her condition, according to the Washington Post.

"I just want them to understand that this is what I'm going through, but you don't quit living," she said. "You keep going."

Experts praised Summitt for sharing her struggle with the public.

"When you're a very public figure and you share something so personal like your own illness, it brings attention to it, and bringing attention to this devastating illness might benefit others," Arvanitakis said. "It could mean more research will be done on it. It will be recognized earlier and people could have access to treatment earlier."

More information

The U.S. National Institute on Aging has more on early-onset Alzheimer's.