Researchers are studying people they call "super-agers" — those 80 and older whose thicker-than-average brains at that age still make them as "sharp as a tack."
Writing in the Journal of the American Medical Association, researchers at Northwestern University in Chicago say the memory skills of "super-agers" are on a par with people in their 50s and 60s.
The experts found that these exceptional elderly patients lose brain volume a lot more slowly than others at the same age, giving them a thicker cortex.
The cortex is the outer layer of the brain where such functions as memory and problem-solving are concentrated.
The experts are not clear about what leads some people to lose brain volume at a slower pace than others. But they believe genetics and growing up in a healthy environment during early childhood may be factors.