She had to watch him now so he wouldn't step in front of cars. He was a dangerous passenger who grabbed the steering wheel or tried to open his door while the car was moving. He shouted swear words and walked constantly, sweeping belongings off tables as he strode. He had hit his oldest son, Andy, a Wilmington architect, and he had hit Joanna.

"Yesterday was the day I reached my own personal limit," she wrote that November, "fighting him to get clothes off, keep him in the shower while I washed him, getting him dressed. I think we've gone back to another good day/bad day cycle, but the good days (today) aren't very good, and the bad days are horrible."

The next month, she decided she could no longer handle him. Rejected as too violent by nursing homes, Moore was admitted to a psychiatric hospital. To Joanna's horror, he rode there in handcuffs.

By spring 2001, she was no longer sure her husband remembered her or other family members. She had decided to decline hospital care if he got sick, choosing hospice, instead. "I know that this was Bob's choice, as well," she wrote. "He is now in the process of dying. I expect the disease will steadily deprive him of his humanity until there is nothing left but the shadow of life. First it took his memory; then it took his dignity; now it is taking his life."

A theory on dementia

A century ago, when German scientist Alois Alzheimer first identified the disease that bears his name, doctors thought dementia was rare. In reality, few lived long enough to get it.

By the time Trojanowski and Lee decided to take on Alzheimer's, the dark side of a lengthening life span was emerging. The longer people's bodies lived, the more often their minds failed.

In 1982, scientists knew little about the diseases that make brains die. They did not even know what made up the plaques and tangles that Alzheimer had seen under his microscope.

Lee and Trojanowski would prove that tangles are made of an abnormal form of the protein tau. Later, they showed how it weakens and kills cells. Other scientists found that plaque contained a different protein, beta-amyloid. In 1998, the protein in Lewy bodies - round clumps found in one part of the brain in Parkinson's patients and in other parts in those with Lewy body dementia - was identified.

Trojanowski and Lee then proposed a unified theory of dementia. All of the dementias, they said, have in common misfolded proteins, that accumulate in the brain. How to derail that process is the billion-dollar question.

Much remains a mystery.

How and why do cells die? What role do the errant clumps of protein play? What makes the diseases appear in more and more of the brain? How can some people have Alzheimer's pathology without symptoms? What triggers violence?

Then there's the key question for Moore's children: What's my risk? For late-onset Alzheimer's, which starts after age 60, there's no easy answer. Genes certainly are a factor, though only one for this type has been found.

One study estimated that 39 percent of people with a parent or sibling who'd had Alzheimer's will eventually develop the disease.

Another of male twins released this month found that genes mattered most, but lifestyle seemed to make a difference. Twins who did not have Alzheimer's when their brothers did tended to have more education. This supports the theory that "cognitive reserve" can help prevent or delay the disease, said the study's author, Margaret Gatz, a University of Southern California psychologist.

Experts say there's no way to predict an individual's late-onset Alzheimer's risk. It's even murkier for other dementias.

"I don't think it means anything to the kids that they can deal with one way or the other," Clark said of the Moore family history.

He could only suggest activities that seem to lower risk: Eat healthy food, exercise, and keep your mind active. Moore's children do all that.

Remaining by his side

It was January 2004, and Joanna arrived at Bob's nursing home to feed him lunch, just as she had almost every day for two years.