Flat on your back, with arms by your side, can cause snoring, which affects half of all adults at some point and is more common the older we get. Snoring isn't just annoying for the person next to you or in a nearby room. It can disrupt your sleep and lead to thickening and problems with the carotid artery, which supplies blood to your brain, face, and neck. This position also isn't a good choice if you're prone to sleep apnea -- shallow breathing or pauses in your breath that prevent restful sleep. Sleeping on your back can lead to a sore lower back as well. There is one big pro to this position, though: It can help acid reflux.