Sharp-witted elderly shed insight on dementia

CHICAGO, 17 nov 2008– People who manage to keep a razor-sharp memory well into their 80s appear to have fewer fiber-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 aging 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 aging 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.

People with Alzheimer's disease have abnormal levels of both plaques and tangles. There is no cure for Alzheimer's, and current drugs merely delay symptoms.

Many drug companies have been working on therapies to remove clumps of beta amyloid from the brains of people with Alzheimer's in the hope of slowing or reversing the course of the disease, but have met with limited success.

Recently, however, some companies have begun to focus on therapies directed at toxic tangles caused by an abnormal buildup of the tau protein.

One, a nasal spray made by Allon Therapeutics Inc, improved some measures of memory in an early-stage study of patients with mild cognitive impairment, a precursor to Alzheimer's.

Rember, made by TauRX Therapeutics in Singapore, improved key measures of thinking and memory in some people with moderate Alzheimer's disease.

Geula said new research will focus on what makes cells in super-aged brains more resistant to tangle formation.

"We want to see what protects the brains of these individuals against the ravages that cause memory loss," he said.

Alzheimer's is the most common form of dementia, affecting 5.2 million people in the United States and 26 million globally, according to the Alzheimer's Association