Intermittent use of bright light to modify the circadian phase

摘要

A method for accurately assessing and rapidly modifying the phase and amplitude of the endogenous circadian pacemaker is disclosed. A circadian cycle modification capacity assessment method comprises (before and after a stimulus) eliminating activity-related confounding factors associated with the sleep-rest cycle which otherwise mask the state of the endogenous circadian pacemaker. Based on either individual or normative assessment data, the circadian phase and amplitude modification method involves the application of bright (about 9,500 lux) light and, advantageously, episodes of imposed darkness, at critically chosen phases to achieve rapid and stable changes in phase and amplitude. The timing of the episodes of bright light may be chosen either by reference to empirically-derived phase response data, or by using a mathematical model in which the endogenous circadian pacemaker is a second order differential equation of the van der Pol type, transformed into two complementary first order equations. A forcing function in the model is substantially proportional to changes in the cube root of the surrounding illuminance, in lux. The amplitude of the endogenous circadian pacemaker may actually be reduced to substantially zero, so as to bring about dramatic phase modifications in diminishingly small periods of time. The methods find special utility in treating "jet lag" sufferers, shift workers, advanced circadian phase experienced by many elderly subjects, and those afflicted with delayed sleep phase insomnia.