This intrinsic oscillator not only governs sleep and wake timing, but also rhythms of temperature, the hormones melatonin and cortisol, mood and cognitive acuity, cardiac, respiratory, and renal function, and most aspects of digestion and detoxification [1].
This circadian phase is best reflected in outputs of the circadian oscillator, such as sleep-wake timing [9], [14].
Although these correlations among mutant animals or extreme chronotypes are promising, it remains unclear how well human period length is predicted from measurements in peripheral tissues in ordinary individuals, and whether these values correlate with sleep-wake timing in vivo.
Future research could test this hypothesis that component exponential processes organize into a power law in physiological systems such as sleep-wake timing (for example, the developmental evolution reported in [3]).
In retrospect, we were interested to know to what extent fibroblast period could predict sleep-wake timing, but our studies were not designed to test this hypothesis and in most cases the rigorous routines of our subjects also controlled sleep-wake.
The variability of sleep-wake timing was remarkably greater in the schizophrenia group than in the control group (Fig. 1).
In this study, we recorded profound abnormalities in circadian sleep-wake timing and in the rise and fall of melatonin levels in people with schizophrenia who have long-standing subjective sleep problems.
According to the ICCs computed in each genotype for the in vitro period data, the higher replicability in PER3 5/5 may indicate that the circadian rhythms in this genotype are more robust, and may be related to the fact that PER3 5/5 homozygotes in one of our previous studies (40) had stronger correlations between melatonin and sleep-wake timing.
Because chronotype, bedtime and wake time are related to food timing, covariance with food timing was further assessed.
Physical activity (counts per minute and intensity categories) and sleep duration and timing (minutes, bed time, wake time) will be measured using ActiGraph accelerometers (GT3X, ActiGraph, Pensacola, FL) worn around the waist over 7 days.
The only instructions that the patients received regarding the timing of light treatment was to administer the treatment shortly after habitual wake time and before noon each day.
