While only an association, not a causal relationship, nevertheless worthwhile acting upon. Interesting that there is a greater association with physical exercise than with mental exercise (e.g., Sudoku), although, again, to play it safe, as well as make life more interesting, both are better. Quote:
…. using imaging scans, the scientists found that the subjects who engaged in the most physical exercise, including walking several times a week, had less shrinkage and damage in the brain’s white matter, which is considered the “wiring” of the brain’s communication system. The relationship remained even after the researchers controlled for things like age, health status, social class and I.Q.
As far as mental exercise, “we can only say we found no benefit in our sample,” said Dr. Alan J. Gow, an author of the study and a senior research fellow at Edinburgh. He added: “There might be associations earlier in the life course. Such activities also have important associations with well-being and quality of life, so we would certainly agree it is important for older adults to continue to pursue them.”