From the June 19, 2003 New England Journal of Medicine:

Use It or Lose It — Do Effortful Mental Activities Protect against
Dementia?
Joseph T. Coyle, M.D.

CHESS NOTES
Author(s): Harold Dondis and Patrick Wolff, Globe Correspondents
Date: August 4, 2003

When Arnold Denker, an octogenarian and a former US champion, wrote a
letter to Chess Life asserting that he had never known a grandmaster
who had developed Alzheimer's disease, it touched off a lot of
discussion.

Denker had forgotten that, by his own narration, his friend Albert
"Bring 'em Back Alive" Pincus had died with Alzheimer's. Nevertheless,
there was a general feeling that it was an exception. Dan Mayers,
another active tournament player in his 80s, wrote a letter to Chess
Life to declare that Denker was correct and that scientific
experiments were necessary to prove it.

We kidded Denker that if he were right, he should receive a Nobel
Prize in medicine. It seemed hard to believe that concentration on
chess games, albeit four to six hours at a time, could in some way
form a physical barrier against amyloid plaques, which trigger
Alzheimer's.

But now the New England Journal of Medicine has published an article
that, in effect, says Denker and Mayer could be right. The Journal
published a study by Joe Verghese and a team at Albert Einstein
College of Medicine in New York in which they followed 469 people over
age 75 beginning in 1980, screening out anyone who had signs of
dementia.

The researchers measured how often the subjects participated in
leisure activities such as reading, walking, dancing, and playing
board games. Then they checked the number who developed signs of
dementia or Alzheimer's, diseases increasingly thought to be similar.

Those who played games, particularly chess and bridge, and those who
played a musical instrument showed, respectively, a 75 percent and 64
percent lower risk of Alzheimer's or dementia.

Crossword puzzle enthusiasts showed a 38 percent lower risk while
fitness buffs, except for dancers, showed no lower risk.

In a commentary in the Journal, Joseph Coyle, a Harvard professor of
psychiatry and neuroscience, took the position that thoughts and
experiences can rewire the brain, creating new synapses and neurons.
If so, this experiment opens new avenues of research on the human
mind.

The study, of course, could be flawed, but the unusually positive
results for bridge and chess players is certainly significant and
startling. When taken with other studies showing that playing chess in
schools increases mental performance, the report makes one sit up and
take notice.