A sleep study is just what it sounds like: a study of your sleep. Known as a polysomnogram, a sleep study measures many different factors involved in sleeping. It is conducted during the night while you slumber in a private and comfortable room. The polysomnogram measures and records breathing patterns, body movement, blood-oxygen levels, muscle activity and heart rhythm… throughout the different stages of sleep. Typically, the sleep study will last 6 to 8 hours.