Lying on the side is the most common sleep position for animals in the wild. New studies from Stony Brook University have found that a side-sleeping position seems to improve clearance of wastes from the brain. Amyloid beta, for example. When it builds up it can form plaques, a telltale characteristic of Alzheimer’s disease. Using dynamic contrast magnetic resonance imaging (MRI) researchers observed the glymphatic pathway of rodents under anesthesia in three different positions: on their sides (lateral position), backs (supine position), and bellies (prone position). The rodents who were in the lateral position cleared amyloid beta about 25 percent better than when in the prone or supine position. Some say sleeping on your left side is a preferred option.