The underlying measurement behind the SmartCap levels is brain activity.
Often referred to as EEG (or electroencephalogram), this brain activity has been the golden standard in sleep science for over a decade. The SmartCap measures this activity and determines a high resolution frequency profile of the signal which spans the delta, theta, alpha and beta frequency bands of EEG. All frequency information is analysed using the SmartCap Universal Fatigue Algorithm to determine a level of alertness, and it has been independently shown that the specific brainwave frequencies used relate to various stages of alertness.
Fatigue as a concept is somewhat grey. Terms such as vigilance, alertness, tiredness and fitness to perform are often used in place of fatigue, all with the same sentiment but subtly different definitions, and none of which consistently correlate with how a person is feeling. What can be said with certainty is that all fatigue incidents that have occurred to date, in any setting, were unintentional. This illustrates that individuals that progress to microsleep are in-fact unaware moments before the microsleep, and also that despite all natural instinct to do so, those individuals were unable to resist progression toward microsleep. As such, we strongly believe that the most relevant safety measure is an individual’s ability to resist sleep (often times despite how they feel) while performing a task. This is what the SmartCap measures, and what it was independently validated to measure.