Like all other animals, humans have a circadian clock, which controls metabolism, physiology, behaviour, and cognition. Traditionally, the human clock is investigated under controlled conditions in the laboratory – in temporal isolation or “forced desynchrony” experiments. Over the past 20 years, we have gained many insights about circadian clocks in controlled laboratory experiments using various model organisms. The Human Chronobiology Group at the IMP now applies these laboratory insights to investigating human clocks in the real world. While the right experimental conditions for a specific circadian question have to be created in the lab, they often already exist in the real world, here are just a few examples:
Light exposure is specific for different regions of the world and can greatly differ between rural and urban settings; social timing (e.g., work or school schedules) is often very different from the biological timing of an individual’s circadian clock (“social jetlag”); many industries use shift-work, enforcing a multitude of schedules on the circadian clocks of approximately 20% of the workforce; many nations run circadian “experiments” by regularly changing social time in spring and autumn (DST).
We use these real-world conditions for circadian research. Their results will lead to a greater understanding of human clock mechanisms and to an increased awareness for the circadian clock in the general population. This will pave the way for solutions, which decrease the detrimental effects of violating circadian timing.
In contrast to laboratory studies, real-world conditions cannot control for the influence of a single factor. But with large numbers and good statistics, one can still identify the main factors and their effect sizes. Our epidemiological approaches provide us with excellent material to investigate the factors that influence chronotype and sleep duration (theWeP) or to study the Genetics of sleep and circadian timing.
Although the real-world approach is extremely powerful, many questions still rely on controlled laboratory settings. Studying the timing of the brain’s cognitive processes, for example, involves powerful imaging methods (BrainTime), and the insights that we gain from measuring sleep and activity in the real world have to be verified in the Sleep lab.