A personal mobile system for self-initiated shifts in Dim-Light Melatonin Onset (DLMO) produced by the automated reporting and reminding of a light exposure/avoidance prescription (LEAP)

Abstract

Two experiments were performed. In the first experiment, 21 subjects (11 female) participated in a 12-day study. After a 5-day baseline period, participants were given 90-minute advanced sleep/wake schedules for one week. Participants were randomly assigned to one of two conditions, an Advanced condition with a light expo-sure/avoidance prescription (LEAP) designed to advance circadian phase or a Delayed condition with a LEAP designed to delay circadian phase. All participants were given wrist-worn activity and light recording devices, which they wore throughout the exper-iment, and all participants were required to have a mobile communications device (i.e. smartphone, tablet, etc.) to maintain constant communications with the experimenter. The experimenter served as a surrogate for the automated system used in the second experiment. After 7 days on the 90-minute advanced sleep/wake schedule, circadian phase advanced 132 ±55 minutes for those subject to the Advanced condition and de-layed 59 ±24 minutes for those subject to the Delayed condition.

The results of the two experiments demonstrate that, using the system and follow-ing the LEAP provided, an individual can, while leading their everyday life, change the timing of his or her circadian clock as measured by dim light melatonin onset (DLMO).

In the second experiment, a single participant followed the instructions presented without human intervention by the prototype wireless light/activity sensor and mobile app. The first 14 days were similar in schedule to Experiment One: after a 7-day base-line period, the participant followed a 7-day, 90-minute advanced sleep/wake schedule, during which time he followed the same LEAP as those in the Advanced condition in Experiment One. On days 15 and 16 he followed an algorithmically-generated LEAP intended to delay him 198 minutes. After day 14, the subject's circadian phase had ad-vanced 57 minutes (subjects in the Advanced condition in Experiment One advanced 132 ±55 minutes); after day 16, the subject's circadian phase had delayed 162 minutes.

This thesis describes the creation of a mobile system to foster self-mediated adjust-ments to one's circadian clock. The adjustments are achieved when the user follows system-provided instructions for light exposure and avoidance. The system also analyz-es current environmental light levels in order to alert the user when the light level is inconsistent with the currently active light exposure or avoidance instruction. The sys-tem consists of a light-exposure-logging device and a mobile application; a prototype of this system was created for this thesis.