Same story as the last post, but with a twist

So, apparently a new article is out touting the benefit of exercise for preventing Alzheimer's and cognitive decline.  Basically it's a correlational study where they interviewed people on how much they walked per week and tracked them over time to measure how much their brains did or did not shrink with age (yes, our brains shrink with age, and this shrinkage may, on average, reflect our cognitive ability, or loss thereof).  They also tested the subjects for cognitive impairment 13 years after the study began (a much better measure than brain shrinkage in my opinion).  As it turns out, walking 72 blocks per week (about 7 miles) is correlated with less brain shrinkage and with less cognitive impairment.  The authors also reported that walking greater than 72 blocks did not seem to confer any additional benefit.  As Dennis Fortier over at the Brain Today Blog points out, the good news in this story is that you may not have to go to the gym or run marathons or take up some other grueling work out routine to keep your brain healthy, a simple, one-mile walk everyday should do it.