Development of ambulatory tools for assessment of human circadian rhythms: an international project
The physiological measures that demonstrate a circadian system (biological clock), such as body temperature or hormone production, can be easily influenced by external or non-circadian factors. For example, eating and exercising both generate changes in core body temperature, which are not reflective of the circadian pacemaker.
As a result, investigating human circadian rhythms may be demanding for the participants since it requires them to remain in the laboratory for extended, uninterrupted stays. The goal of this study is to validate new methods of collecting information on the expression of human circadian rhythms without a mandatory laboratory visit.
Circadian oscillation of clock genes in humans and resetting by environment cues
The hypothalamus suprachiasmatic nuclei (SCNs), a specialized region in the brain, are responsible for the generation of many circadian rhythms and play the role of master biological clock. This central clock is connected to other regions of the brain and other parts of the body. Certain genes, which are necessary for the function of SCNs cells, are also expressed outside of the central clock.
Thus, secondary or peripheral, clocks exist, in addition to the central clock in the SCN, in other parts of the body. What could it mean for the gut or the immune system to have a clock? How do central and peripheral clocks interact? The Centre investigates the peripheral circadian clocks that exist in human tissues.
Workers on rotating shift work: study of complementary fatigue management approaches
In many cases, shift work implies that the worker must be alert at times of day that are not favourable. The night shift worker, for example, may be required to work when the circadian pacemaker says “sleep” and vice-versa.
Certain principles of circadian physiology, such as the powerful effect of light on the biological clock, can be applied to help shift workers adapt to their schedules. This study applies principles of circadian and sleep hygiene to workers on rotating shifts.
Circadian modulation of sleep and mood in bipolar affective disorder
The circadian pacemaker significantly affects the pattern of sleep and waking throughout the day: making some times of day more favourable for sleep than others. Sleep disturbances such as insomnia or hypersomnia have been observed in patients with bipolar affective disorder, and can often precede relapses into mania or depression.
Circadian rhythm disturbances have also been associated with this disorder. Using a procedure based on an ultra-rapid sleep-wake cycle (patients are asked to maintain a schedule of alternatively attempting to sleep and wake up several times per day), the Centre evaluates how the circadian pacemaker modulates sleep and mood in bipolar patients.
Simulated travel across time zones and treatment by ordinary indoor room light
Travel across time zones is often associated with feelings of malaise or maladaptation, particularly in the first days of the new time zone. In the time isolation laboratory, we perform simulated travels across time zones in healthy young men and women. This study tests the sensitivity of the circadian pacemaker to ordinary indoor levels of room light as a means to promote the adaptation of circadian rhythms to the new “time zone”.
Prevention of physiologic maladaptation to shift work
A misalignment of the circadian clock with the night work schedule can underlie the reduction in night time alertness and the abbreviated daytime sleep often experienced by night shift workers. This study tests whether a light intervention including night time bright light phototherapy can better align the internal clock of night shift workers with their time of work and sleep/wake schedules.
