Joseph Engh was visiting his father in San Francisco six months ago when he noticed something was wrong.

His 89-year-old father, Moy Ng, seemed surlier than usual, and a little forgetful. Ng had developed pneumonia, which had prompted Engh's visit, so Engh took his father to see his doctor.

Ng, it turned out, has Alzheimer's disease - he might have had it for months or even years. But Ng lived alone, and with no family or close friends around to notice his memory loss or personality changes, getting him diagnosed and treated was a challenge.

"The doctor had known for some time that my father was having a problem. But he kind of refused to get diagnosed," said Engh, 63, who lives in Seattle.

Roughly 800,000 people in the United States haveis at risk, adult protective services should be contacted, he said.

"I would talk to the person first, but don't leave it at that," Boxer said. "If, in your heart of hearts, you're worried they're not fine, you should take it a step further. I'd rather be wrong and embarrass the person a little bit than to miss this. ... You have to be tough in these situations."

That's what Engh is learning now. His father, he said, was always difficult, but he gets angry, and sometimes even violent, when he's reminded of his Alzheimer's diagnosis.

Engh realized that he couldn't leave his father entirely on his own, so at least for now, he lives part time in San Francisco to be near him - to take him to doctors' appointments,