Measuring Sleep by Wrist Actigraph

A convenient method of monitoring personnel sleep and activity in field conditions is needed to promote medical planning for modern combat. In the period from April 1980-March 1981, we have programmed, tested, and begun evaluations of a wearable digital activity system, and we have refined a computer process for recognizing sleep from this system. Together, these efforts enable us to collect data from freely ambulatory subjects which can be scored automatically for sleepwake with accuracy comparable to EEG scoring. The system is ready for miniaturization leading to field use. Our microprocessor-based digital activity monitor was built to our specifications, and we added external activity and illumination transducers, Actual data collection was implemented and 25 records totaling over 27,000 minutes have been obtained as of March, 1981. Fourteen records 12,739 minutes collected with the digital monitor were scored retrospectively with 93.6 agreement with EEG sleepwake scoring. Research is continuing to further increase the accuracy of the sleep recognition algorithm. Since the errors that occur include both mis-scoring sleep as wake and vice versa, they tend to cancel. Correlations between sleep durations scored from activity data and from EEG records were r0.9760 for digital monitor data. Current results now allow us to specify design criteria for a miniaturized wrist-mounted activity monitor suitable for field or combat use.