Sharp-witted elderly shed insight on dementia

CHICAGO (Reuters) - People who manage to keep a razor-sharp memory well into their 80s appear to have fewer fibre-like tangles of a protein linked with Alzheimer's than those who age normally, U.S. researchers said on Sunday.

Lower levels of this protein, known as tau, appear to be a critical factor in maintaining memory skills, they said.

"It was always assumed that the accumulation of these tangles is a progressive phenomenon through the ageing process," Changiz Geula of Northwestern University's Feinberg School of Medicine in Chicago, said in a statement.

"But we are seeing that some individuals are immune to tangle formation and that the presence of these tangles seems to influence cognitive performance," said Geula, who is presenting his findings at a Society for Neuroscience meeting in Washington.

While most studies of memory and ageing involve people with some form of cognitive decline, Geula studied the so-called "super-aged," or those who maintain sharp cognitive skills in advanced age.

The researchers studied the brains of five deceased people considered super-aged because of their high scores on memory tests at age 80, and compared them to the brains of elderly individuals who had no signs of dementia.

They found far fewer tau tangles in those who had sharp memories than those with normal memories for their age.

Curiously, the number of sticky plaques made of beta amyloid-- considered a hallmark of Alzheimer's disease -- was about the same in both groups.

While tau protein accumulates inside brain cells, forming fibrous tangles that eventually cause the cell to burst, beta-amyloid plaques accumulate outside the brain cell, disrupting cell-to-cell communication.