A method for quantitative sleep characterization includes acquiring a surface electroencephologram (surf-EEG) signal from an individual by a probe, decomposing the surf-EEG signal into a plurality of intrinsic mode functions (IMFs) by a computer processor in communication with the probe, wherein the plurality of IMFs comprises a first group of IMFs and a second group of IMFs, calculating a ratio comprising an amplitude or power of at least one of the IMFs in the first group in the numerator and a corresponding amplitude or power of at least one of the IMFs in the second group in the denominator; and identifying a period in the surf-EEG waveform as slow wave sleep (SWS) if the ratio associated with the period is above a predetermined threshold.