Shrinking Brain Part, Men’s Age Linked

You get old. You may lose your teeth. You may lose your hair. And, according to a Canadian psychiatrist, if you are a man, you may also lose a big chunk of brain tissue.

In a finding that seems destined to spark new battles in the war between the sexes, a recent study found that a part of the brain gets smaller with age in men--but not in women.

The brain part, known as the corpus callosum, is a broad, arched band of about 300 million nerves through which the left and right hemispheres of the brain communicate.

The research also confirmed what almost all previous studies of the callosal area have shown--that men tend to have more brain tissue in that area than women to begin with.

There is no evidence that less or more callosum makes the brain less or more effective, researchers said.

In a letter to the New England Journal of Medicine, Sandra F. Witelson, a professor of psychiatry at McMaster College in Ontario, Canada, said she had based her conclusion on reports of 62 autopsies conducted on men and women.

She found a 20% loss of callosum, on average, among men between ages 61 and 70, compared to men between 25 and 50.

There was no deterioration among the women, Witelson said. She noted that such shrinkage may begin in women after they have passed the age of the oldest female study subject, which was 68.

For men and women combined, the correlation between the size of the corpus callosum and age was virtually undetectable, “which may be why little or no correlation has been observed in previous studies,” Witelson said.

One big question remains unanswered.

“Whether cognitive changes accompany the anatomical changes in men remains to be determined,” Witelson said. “If so, such results would indicate different courses of cognitive change with age in men and women.”

In other words, men’s brains get smaller but there’s no evidence that their brains function less well.

“A 20% loss of tissue in some areas doesn’t mean a lot, while in other areas it may mean everything,” said Dr. Bruce Cohen of McClean Hospital in Belmont, Mass., one of the world’s foremost brain research institutions.

“If it were a particular set of fibers going from one side to another, it could make a lot of difference,” Cohen said in an interview.

“Depending on which set was showing the loss, you could be looking at something which is very biologically significant or something that you wouldn’t otherwise notice in behavior or any cognitive ability,” he said.