The search for an effective, easy-to-use treatment for sleep apnea has been going on for years. The gold standard is a breathing machine known as continuous positive airway pressure (CPAP). A report published online this week by JAMA Internal Medicine describes a mouth-guard-like device that may work for people with mild sleep apnea, but that may not be much help for those with severe sleep apnea. The 18 million Americans with obstructive sleep apnea sufferers are a powerful incentive for device manufacturers, and there are myriad alternatives to CPAP in the marketplace and under development. Swedish researchers tested a custom-fitted mandibular advancement device among people with self-reported sleep apnea. It worked, but a placebo device worked almost as well.