Two fresh studies strengthen the case that physical activity protects the aging brain from decline. Walking a couple of miles a day at a moderate pace appears to make a difference.
Past studies have linked both physical and mental inactivity in adulthood with elevated risk of Alzheimer's disease (SN: 3/10/01, p. 148: http://sciencenews.org/articles/20010310/fob1.asp). A regimen of stepped-up physical activity can cause greater blood flow in the brain and stronger performance on mental tests (SN: 2/21/04, p. 115: http://sciencenews.org/articles/20040221/fob1.asp), but whether regular exercise can fend off subsequent cognitive decline has remained a question.
Furthermore, if physical activity indeed guards the brain, the question becomes, How much is required to achieve benefits?