Not sure why you�re so tired today? You might have taken a stroll at 3 a.m. Stanford researchers have found sleepwalking is more common than previously believed. Almost one-third of Americans report walking in their sleep at some point in their lives, and 3.6 percent have done so in the past year. About 1 percent take a nighttime saunter two or more times per month, according to the findings published this week in the journal Neurology. (Do you work out less often than that? Get fit today! Shred your excuses with these 15-Minute Abs, Arms, and Chest Workouts.)