A method and apparatus monitors chronic disease state of a patient. The method may include extracting, in a processor, for each of a plurality of monitoring sessions, a respiratory feature from a respiratory signal indicative of the patient's respiration during the monitoring session, the respiratory signal derived from at least one sensor； and computing, in a processor, a stability measure of the patient for a monitoring session, the stability measure representing an indication of a change point having occurred at the monitoring session in a statistical distribution of the respiratory feature.
