Patent ID: 8781796

Claim:
A method for estimating alertness of a human subject implemented by a processor, the method comprising: receiving initial values for a plurality of model variables of a mathematical model, one or more of the model values comprising variables which specify or estimate probability distributions, the model variables including: one or more individual trait variables, each individual trait variable comprising a parameter that is unique to the subject and which is generally constant over time; and one or more individual state variables, each individual state variable comprising a time varying parameter; receiving a sleep history input indicative of the subject's asleep and awake status between a first time and a second time; identifying, by the processor, one or more transition time points within the sleep history, each transition time point corresponding to one of: the subject's transition from awake to asleep status and the subject's transition from asleep to awake status; dividing, by the processor, a time between the first time and the second time into a plurality of time segments, each time segment extending between: a corresponding time segment start time which is one of: the first time and one of the one or more transition time points; a corresponding time segment end time which is one of: the one or more transition time points and the second time; each time segment also associated with a sleep status value as indicated by the sleep history; initializing, by the processor, the model variables at the first time to be the received initial values; for each time segment, starting at a first time segment whose time segment start time corresponds to the first time through to a last time segment whose time segment end time corresponds to the second time: using the model, by the processor, to estimate values of the model variables at the time segment end time, using the model comprising: configuring the model based at least in part on the sleep status value of the time segment, and basing the estimated values of the model variables at the time segment end time on the values of the model variables at the time segment start time and a duration of the time segment; and for time segments other than the last time segment, setting, by the processor, the estimated values of the model variables at the time segment end time to be the values for the model variables at the time segment start time of a next time segment; and estimating, by the processor, alertness values of the subject at the second time based at least in part on applying the model to the values of the model variables at the second time.