The sleep estimation algorithms in our software were validated for estimating sleep in a standard sleeping environment. They have not been validated for naps or "micro-sleeps", which can take place during the course of the day. The problem with actigraphic estimates of sleep is that one is dealing with a single channel of simple information. It is impossible for the actigraph to distinguish between periods of extreme inactivity (reading, TV watching) and sleep during the course of the day. What makes the nighttime estimates of sleep possible is the assumption that sleep is the intent during that period of time (based on event markings, logs, etc.). With knowledge that the subject is in bed and TRYING to sleep, the estimates of sleep from activity can be used with much more confidence. This does not mean that the actigraph cannot be used to examine daytime sleepiness; but one cannot say, with any certainty, that an inactive period is asleep. Solution? Don't report these periods as naps. Don't report them as Micro-Sleeps. Refer to them as daytime periods of inactivity. Show that one group has more of these periods than another or that the patterns of same group change with intervention. Let the reader draw his/her own conclusion. Given enough subjects and a large enough change in the number and duration of these periods of inactivity the results can be quite impressive, especially when one considers that the more rigorous alternatives (portable EEG or videotaping) are much more difficult (if not impossible) in most populations.

Depending on the Mode of Operation selected, information derived from the conditioned analog signal is processed in different ways to provide information about the subject's motion.