A study by researchers from the University of Michigan showed that the human body's internal biological clock remains closely linked to the changing seasons and the length of day and night, defying the effects of modern life.
Study: Our biological clocks are linked to the changing seasons
Regarding the subject, Dr. Ruby Kim, the lead researcher in the study, said: "We humans are still really creatures dependent on the changing seasons, even if this is not obvious in our daily lives. Our study showed that human physiology is unequivocally affected by the length of daylight, including how we adapt to changes in our daily routines."
The study relied on analyzing sleep data collected from thousands of resident physicians working shifts in hospitals, who use smartwatches and wristbands. These physicians work on a shift system, meaning their sleep schedules are disrupted and far from normal.
The study results showed that the daily rhythms of doctors were subject to clear seasonal changes; for example, doctors were found to sleep for longer periods in winter and shorter periods in summer.
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To explain these observations, the research team proposed a fascinating new model of the human circadian rhythm. This model posits the existence of two separate biological clocks: one that tracks dawn and another that tracks dusk, and that these two clocks interact with each other.
Professor Daniel Forger, co-author of the study and director of the Center for Applied Mathematics at the University of Michigan, explained: "People usually think they have one internal clock. But in reality, there are two, as if they interact with each other, and the two clocks are affected by the different seasons and the duration of natural light exposure."
The research didn't stop at analyzing sleep behavior; it extended to include analyzing the participants' DNA. The results revealed that genetic variations influence a person's activity level and their ability to adapt to changes in day length and sleep schedule.
The study authors believe their findings open new avenues for understanding seasonal affective disorder (SAD), a form of depression linked to shorter days. The results also shed light on the underlying mechanisms of anxiety, sleep disturbances, and metabolic disorders, paving the way for the development of future preventative and therapeutic strategies.
