If you can walk a quarter-mile, odds are you have at least six years of life left in you, scientists announced today. And the faster you can do it, the longer you might live. While walking is no guarantee of health or longevity, a new study found that the ability of elderly people to do the quarter-mile was an "important determinant" in whether they'd be alive six years later and how much illness and disability they would endure. "The ability to complete this walk was a powerful predictor of health outcomes," said study leader Anne Newman of the University of...