Circadian factors

Circadian factors - single time-point studies adequate ... 

Fosnaugh, J.S., Bunker, E.B., and Pickworth, W.B., Daily variation and effects of ambient light and circadian factors on the human light reflex, Meth. Find. Clin. Exp. Pharmacol., 14, 545, 1992. 

As alluded to earlier, circadian factors have also been implicated as a contributing factor to traffic accidents. However, the interaction between circa-... 

B. Work-Related Issues That Affect Sleep and Circadian Factors... 

Predictability provides an individual with the opportunity to plan, whether for work, recovery requirements, or home activities. When possible, schedule stability provides more consistent circadian cues and the opportunity to create individual patterns and habits that minimize the physiological disruptions. Modem work demands, especially 24/7 requirements, are often associated with overtime, which may be elective or on occasions required. Extending work has the potential to increase the continuous hours awake, be affected by circadian factors by working through a window of circadian low, and contribute to both acute sleep loss and a cumulative sleep debt. The timing and amount of overtime and whether it is elective or required, can all affect the level of physiological disruption. 

Recent experiments (4) have shown that there are no significant age or gender-related differences in thermal environment preference when all other factors such as weight of clothing and activity level are the same. Whereas people often accept thermal environments outside of their comfort range, there is no evidence that they adapt to these other conditions. Their environmental preference does not change. Similarly there is no evidence that there is any seasonal or circadian rhythm influence on a person s thermal preference. 

Clock gene and transcription factor with histone acetyl-transferase (HAT) activity that (in complex with BMAL1) constitutes a positive limb of molecular circadian oscillators. 

Folate and FAD are also components of cryptochromes, proteins widespread in living organisms. Cryptochromes are considered photolyase sequence homologues with no DNA repair activities but with blue light-activated factors. Cryptochromes regulate growth and development in plants and seem to be responsible for the synchronization of circadian rhythms in animals and human. ... 

One of us examined the timely use of three factors (melatonin treatment, exposure to light, physical exercise) to hasten the resynchronization of the sleep-wake cycle in a group of elite sports competitors after a transmeridian flight across 12 time zones (Cardinali et al. 2002). Outdoor light exposure and physical exercise were used to cover symmetrically the phase delay and the phase advance portions of the phase-response curve. Melatonin taken at local bedtime helped to resynchronize the circadian oscillator to the new time. Individual actograms taken from sleep log data showed that all subjects became synchronized in their sleep to the local time in 24-48 h, well in advance of what would be expected in the absence of any treatment (Cardinali et al. 2002). More recently, a retrospective analysis of the data obtained from 134 normal volunteers flying the Buenos Aires - Sydney transpolar route in the past 9 years was published this further supports such a role for exogenous melatonin in resynchronization of sleep cycles (Cardinal et al. 2006). 

The QT interval is a dynamic physiological variable depending on multiple factors such as cardiac cycle length (heart rate), autonomic nervous system activity, age, gender, plasma electrolyte concentrations, genetic variations in ion channels involved in cardiac repolarization. In addition, circadian and seasonal variations of the QT interval have been described [93]. 

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