I found this very interesting article on msnbc.com about how high cholesterol and borderline high cholesterol seems to have a significant correlation with Alzhiemer's and dementia. Remember that a correlation means these two seem to occur together, but we don't know why or if there's a real relationship there. We may find out later that these findings are coincidental, however I think it's worth looking at. Runners may be at an advantage here since regular exercise encourages good cholesterol while lowering bad cholesterol.
Who knew we crazy runners were really protecting our brains?