From a biological signal detected by a nondestructive sensor, a breath signal, a heart beat signal, and a biological signal intensity are detected. A signal extracted from these or a parameter calculated from this signal is used as an index value so as to provide a sleep stage judgment method and a judgment device. The method and the device are used for judging the sleep stage of an examinee who is sleeping. The device includes a nondestructive sensor arranged on a bed for detecting a biological signal, detection means for detecting hear beat, breath, a biological intensity signal, and the like from the output of the nondestructive sensor, and index value calculation means for evaluating the autonomic nerve from a power spectrum density obtained by subjecting the R-R interval signal detected from the heart beat signal to the Fourier transform and calculating the index value of the sleep stage. By using a plurality of parameters as index signals and a threshold value according to the sleep stage is calculated from data of a predetermined time for each of the index signals, thereby judging the sleep stage. Similarly, a sleep stage judgment method and judgment device using at least one of the parameters calculated from the nondestructive sensor signal as an index value are also disclosed.
SLEEP STAGE JUDGMENT METHOD AND JUDGMENT DEVICE