Initial demonstration of the accuracy and utility of an ambulatory, three-dimensional body position monitor with normals, sleepwalkers and restless legs patients

Objective: To evaluate the accuracy and provide a pilot demonstration of the clinical utility of the BodyTrac, a new, ambulatory device that identifies body position and records and stores this data for a period of over 2 weeks. Background: Diagnosis and treatment evaluation of behavioral sleep-related events (BSREs) that occur with the major parasomnias such as sleepwalking, night terrors and REM behavior disorder have been hampered by the problems inherent in recording relatively rare events which are mostly not recalled by the patients. The number, time of occurrence and pattern of motor behavior for these events has, therefore, never been adequately described. Even the amount of nocturnal walking associated with the restless legs syndrome (RLS) has been hard to specify given the usual problems of night to night variability and in obtaining accurate, subjective reports. The newly developed BodyTrac monitor, by recording body position once every 30 s during a sleep period, provides an enabling technology for evaluating BSREs and may also enhance evaluation of nocturnal waking activities of RLS patients. Design and methods: Three test protocols were completed: an analog-type laboratory test of the BodyTrac's accuracy, an evaluation of seniors with and without sleep disorders, and, finally, evaluation of adult sleepwalkers and RLS patients including a full-night sleep lab assessment. The last two procedures also included monitoring in the home environment. Results and conclusions: The BodyTrac reliably and accurately identified both the wearer's body position (93% agreement with observer) and BSREs (sensitivity = 100%, specificity = 94 - 100%.) Patients were able to wear the BodyTrac during sleep in their home environment with minimal discomfort. The pilot data here suggest that some sleep walkers may have many small BSREs in addition to the larger events that are usually the only ones known to occur.