Estimating sleep cycle using body movement density

The rate at which body movement occurs during sleep is an important element in the estimation of sleep stages. Thus, "body movement density (BMD)", the number of body movements that occur over a period of time, can be used as an index reflecting the quantity of actual body movements measured using an infrared motion sensor. In the present study, sleep stage determined by polysomnography (PSG) as the main physiology index is compared to body movement data. The stages of sleep follow the international standards of Rechtschaffen and Kales. The transitions between sleep levels within the sleep cycle and changes in BMD were synchronous. Using the proposed method, a concordance rate of 76.9% (SD±24.0) between the BMD cycle and sleep cycle was obtained. Therefore, estimating the changes in sleep cycles is possible using only BMD.