All children between ages 6 months and 6 years have sleep problems such as night terrors or bed-wetting. Over time, these issues usually work themselves out, but for 30 percent of children, sleeping for six consecutive hours remains problematic. This lack of shut-eye may be a health threat. In a study of 1,138 children, more than a quarter of kids who didn’t get enough sleep had a weight problem. Why? Fewer hours of sleep boosts production of a hormone that increases appetite and cuts production of one that reins in appetite.