A method of monitoring the status of a patient comprising the steps of: continuously measuring a plurality of patient vital signs to provide a succession of multi-parameter vital signs observations, comparing each successive multi-parameter vital signs observation to a first statistical model being a population-based reference model mapping the probability distribution of multi-parameter vital signs observations for a population of different individuals, calculating a first numerical index based on the probability density of the current multi-parameter vital signs observation obtained by comparison with the first statistical model, wherein an increased value of said index represents an increase in abnormality with respect to the first statistical model, and outputting, on an apparatus output, an alert notification if the first numerical index exceeds a first threshold; characterized by: comparing each successive multi-parameter vital signs observation to a second statistical model (5, 7) being a patient-specific model which is a probability distribution based at least partly on previous multi-parameter vital signs observations for the patient being monitored, calculating a second numerical index based on the probability density of the current multi-parameter vital signs observation obtained by comparison with the second statistical model (5, 7), wherein an increased value of said index represents an increase in abnormality with respect to the statistical model (5, 7), and outputting a status change notification if the second numerical index exceeds a second threshold; and by the method further comprising the step of updating the patient-specific model using the most recent multi-parameter vital signs observation only when the comparison of the most recently received multi-parameter vital signs observation with the population-based model indicates that the observation is within a predefined normal region of the population-based model. continuously measuring a plurality of patient vital signs to provide a succession of multi-parameter vital signs observations, comparing each successive multi-parameter vital signs observation to a first statistical model being a population-based reference model mapping the probability distribution of multi-parameter vital signs observations for a population of different individuals, calculating a first numerical index based on the probability density of the current multi-parameter vital signs observation obtained by comparison with the first statistical model, wherein an increased value of said index represents an increase in abnormality with respect to the first statistical model, and outputting, on an apparatus output, an alert notification if the first numerical index exceeds a first threshold; characterized by: comparing each successive multi-parameter vital signs observation to a second statistical model (5, 7) being a patient-specific model which is a probability distribution based at least partly on previous multi-parameter vital signs observations for the patient being monitored, calculating a second numerical index based on the probability density of the current multi-parameter vital signs observation obtained by comparison with the second statistical model (5, 7), wherein an increased value of said index represents an increase in abnormality with respect to the statistical model (5, 7), and outputting a status change notification if the second numerical index exceeds a second threshold; comparing each successive multi-parameter vital signs observation to a second statistical model (5, 7) being a patient-specific model which is a probability distribution based at least partly on previous multi-parameter vital signs observations for the patient being monitored, calculating a second numerical index based on the probability density of the current multi-parameter vital signs observation obtained by comparison with the second statistical model (5, 7), wherein an increased value of said index represents an increase in abnormality with respect to the statistical model (5, 7), and outputting a status change notification if the second numerical index exceeds a second threshold; and by the method further comprising the step of updating the patient-specific model using the most recent multi-parameter vital signs observation only when the comparison of the most recently received multi-parameter vital signs observation with the population-based model indicates that the observation is within a predefined normal region of the population-based model.