Abstract: Systems and methods for monitoring brain health include determining baseline health of a subject through clinical assessment. A first plurality of observables of the subject across a period of time, comprising a plurality of time intervals, is obtained. Also obtained is a second plurality of observables of the subject across the period. The first and second observables are each one of sensor measurements, measurements of one or more analytes, physiological measurements, and subjective observations. For each time interval, at one least observable in the first plurality of observables and in the second plurality of observables taken during the interval is used to compute a respective brain health index value set for the subject comprising two or more of a motor skill, cognitive skill, mood, and sleep status. A brain health trajectory is determined through comparison of these value sets to the baseline health of the subject at each time interval.