LEESBURG, Fla. - Doreen Watson-Beard cared for more people with dementia than she could count. The nurse was so moved by her patients that she led Alzheimer's support groups. She knew the warning signs and understood there was no cure.

But the 49-year-old never thought the disease would affect someone her age.

The first clues surfaced around five years ago, when she was 44. She'd forget to pick up her grandchildren at school or plans she made with her husband. She wrote down the wrong medication dosage for a patient. "I have no idea what's going on," she remembered telling her doctor.

About 200,000 Americans under 65 are among the 5.4 million Americans suffering from Alzheimer's disease, according to the Alzheimer's Association. Experts' estimates suggest there's a similar number of younger people with other types of dementia, meaning about a half-million Americans, some as young as their 30s, suffer from early-onset or younger-onset dementia.

The number of people suffering from all types of dementia is rapidly increasing because of the aging of the baby boom generation - the 78 million Americans born between 1946 and 1964 - though there's no sign the percentage of younger people with dementia is going up. Pat Summit, the 59-year-old Hall of Fame college women's basketball coach, is among the most famous to suffer publicly with it.

Watson-Beard is one of a tiny minority, a fascinating, sorrowful subset to a disease trademarked by its slow, cruel overtaking of the mind.

Watson-Beard says she was diagnosed two or three years ago; she has trouble remembering the exact time. Forgetfulness was one of her first symptoms; her husband would ask if she was ready to leave and she'd have no recollection they made plans. She became less socially conscious, hanging up abruptly with her boss in the middle of a conversation she thought was finished.

She kept going to work at an assisted living facility near her central Florida home, while caring for her husband, who had liver cancer. She dismissed the symptoms as stress. When her husband died about three years ago, the symptoms continued. She thought it was grief. But it wasn't getting better.

"I thought if I ignored it long enough, it would go away," she said.

Problems at work began cropping up, too. Once, Watson-Beard couldn't figure out how to do a complicated wound dressing - something she'd done many times before. Another time, she wrote down the wrong dosage of a medication on a patient's discharge plan - luckily, that mistake was caught by a pharmacist.

Worried someone might be harmed, she went to the doctor.

She was informed she had dementia, though her doctor has not yet classified it more specifically as Alzheimer's, dementia's most common form. She was told to prepare for the future.

"You might need to get some things in order," Watson-Beard remembers being told.

Dr. Marc Agronin, a geriatric psychiatrist at Miami Jewish Health Systems and author of "How We Age," says symptoms of dementia in a younger patient can be glaring. But diagnosis is often complicated by the fact that it's so uncommon in younger patients and that so many other conditions could cause the symptoms.

Agronin sees no evidence of an increasing rate of early-onset dementia, but there is increased interest. At the memory clinic he runs at Miami Jewish, he has seen an uptick in younger patients concerned their memory lapses mean they have Alzheimer's. They're almost always wrong.

When they're not, the diagnosis can be devastating.

"It's very distressing because they come in and they have young spouses and some of them have kids in grade school," Agronin said. "It's frightening to see someone so young becoming so impaired."

Beth Kallmyer, a social worker at the Alzheimer's Association, said younger people with dementia often get incredulous reactions from others when they share their diagnosis. Many don't realize the disease can affect those who aren't very old.

Kallmyer notes it also frequently forces people to quit their job during their top earning years.

"It can be financially devastating," she said.

That has been true for Watson-Beard. She left her assisted-living job last year and worked briefly as a home health care aide before quitting. She tried shifting to other jobs that didn't involve direct patient care, but her symptoms persisted.

Her house is in foreclosure and she has no medical insurance. She pays out of pocket for doctor's visits and gets her supply of Namenda, which treats dementia symptoms, free from the drug company.

Watson-Beard lives in a brick ranch with pale yellow shutters on a quiet street in this small central city. A few light wrinkles around her eyes are the only main signs of age. She occasionally glances to the left in silence, unable to find an answer in her memory, but she speaks with lucidity most of the time in an interview. But not all days are so good.

Once recently, she came out of her grandchildren's school and went into another unlocked car. It wasn't until the key didn't fit that she realized it wasn't hers. She has had car accidents, once forgot a grandson at a snack bar, and regularly bumps into people who know her but whom she can't remember anything about.

"It's frustrating because you're at this level of functioning and then it's gone and you don't know what tomorrow's going to bring," she said.

She remembers one man in particular now from her years of nursing; he came each day to visit his elderly wife, who was fading away into advanced dementia. She had lost the ability to speak, but her husband wondered aloud if maybe she had entered some higher realm, a new level of spirituality where she no longer needed words.

She used to lead two support groups for the Alzheimer's Foundation of America, but gave one up when she kept getting their locations confused. She still leads one at an assisted living facility in Leesburg.

Those who gather don't know of their leader's diagnosis. She simply sits and listens to their struggles.

For an hour, the group remains in a circle, the clock slowly ticking as the stories flow out. Watson-Beard looks forward to it ending; she prefers to be home.

Watson-Beard wonders if the spiritual life envisioned by her patient's husband is what's in store for her instead of what she imagined aging would be like: staying close to home, enjoying family, going to neighborhood barbecues.

All she knows is that life won't go the way she planned.

"It's not what I envisioned at all," she says, as tears begin again to flow. "It just wasn't in the equation."