Women's brains appear "years younger" than men's, study finds

Women tend to outlive men and stay mentally sharp longer, and a new study out Monday could explain why: female brains appear on average about three years younger.The study enrolled 121 women and 84 men, who underwent PET scans to measure brain metabolism, or the flow of oxygen and glucose in their brains.Like other organs in the body, the brain uses sugar as fuel. But just how it metabolizes glucose can reveal a lot about the brain's metabolic age.Subjects ranged from their 20s to 80s, and acros