Nearly one-third of kids experience sleep issues at some point in their lives, but about 2 to 4 percent have structural defects that cause breathing difficulties during sleep -- often marked by snoring, gasping for breath, or pauses in breathing. The condition, called sleep apnea, is being treated more frequently at Boston Children’s, and other pediatric sleep centers due to increased screening by pediatricians — who are advised by the American Academy of Pediatrics to ask about snoring at well visits — and a tripling in pediatric obesity, a known risk factor for sleep apnea.