While weight is a risk factor my doctor said that close to half of his patients are of normal or below normal weight. Age is also a risk factor. Genetics is the largest risk factor. Something else many people don't realize is that the distilled water thing is mostly to prevent mineral buildup inside the tank, not inside you. The water enters you as vapor and carries no minerals with it. So while you may ruin the humidifier after a while, you won't ruin you. A cpap won't cure apnea but it will allow the many symptoms to heal over time. Not sure why but I don't need the humidity when camping, don't miss it at all, yet at home I need a high setting. On some machines the humidifier will not work on battery.