The anguish of Alzheimer's in a sprawling extended family in Columbia may be hardest on those still lucid enough to know they have it, or those who know they could.
Blanca Nelly Betancur's family is rife with people dangerously close to the age when dementia begins, including Ms. Betancur, 41, and her 11 siblings.
Two sisters already have symptoms of the disease inherited from their mother. They deny it. But her oldest brother, William, 48, knows he is unraveling.
"Five minutes later, I won't remember what you told me," said Mr. Betancur, soft eyes shining sadly, watching himself slip away, Forced to quit his bus driver's job, he started drinking, becoming "irritable and violent," his wife said.
Recently, he told an American researcher: "I've got Alzheimer's. There's nothing you can do for me, but can you sort something out for my children?" But the next day, Mr. Betancur said, "I didn't meet with any scientists."
Fear grips the still healthy siblings. One sister, Gladys, 36, is too afraid to have children, and said her boyfriend announced that if she had the mutation, "he would leave me immediately," saying, " 'I'm not going to look after you.'"