One headline reads "Doing Puzzles 'Could Speed Up Dementia.'" Another, "Brain Exercise Helps Stave Off Dementia." They're both about the same new study out in Neurology this week. So which is it? Both are shades of the truth, actually. Here's what the scientists actually found: Robert Wilson and his colleagues have been tracking more than a thousand people as part of their long-term study, begun in the early 1990s. The patients were 65 or older and the scientists interviewed them every three years.