Why do we still change the clocks if it may negatively affect our health?
This is primarily a historical legacy. Clock changes were introduced to make better use of daylight and save energy. The first large-scale implementation took place during the First World War in Germany and Austria-Hungary. The practice later returned during periods of energy crises, among other occasions. In Poland, regular clock changes have been in effect since 1977.
From a physiological and medical perspective, changing the clocks twice a year is not beneficial. It disrupts our internal biological clock. We can move the hands of a clock by an hour in a second, but there is no magical button in the human body that instantly adjusts all physiological processes to a new rhythm.
How does our biological clock work and why does even one hour matter?
Our bodies function according to a circadian rhythm that lasts approximately 24 hours. Its exact length is individual and depends, among other factors, on genetic predispositions. The most important factor regulating this rhythm is light. It helps synchronise the biological clock with the natural cycle of day and night.
Changing the time requires adjustments in hormonal processes, including the secretion of melatonin, which regulates sleep, and cortisol, whose natural rise in the morning helps us wake up.
The spring time change is the most unfavourable, as it causes us to lose an hour of sleep. It can be compared to travelling eastward and experiencing jet lag. During this period, an increased risk of cardiovascular problems, as well as road traffic and workplace accidents, has been observed. The autumn time change is usually tolerated better, although shorter days and reduced exposure to sunlight may negatively affect our well-being.
Do we all experience the time change in the same way?
No. Much depends on our chronotype, meaning our natural preference for sleeping and being active at particular times. We usually distinguish between larks, who prefer waking up early, and owls, who function best in the evening and at night. Most people, however, fall somewhere between these two groups.
People with a late chronotype tend to struggle the most with time changes, particularly the spring transition. This also applies to adolescents, who naturally tend to fall asleep and wake up later. From a biological perspective, starting school later would therefore be beneficial.
We should also mention the phenomenon known as social jet lag. This refers to the discrepancy between our sleep schedule on work or school days and at weekends, when we often try to make up for lost sleep. Even a difference of one or two hours can disrupt the synchronisation of our biological clock with social time, affecting our daily functioning and potentially leading to negative health consequences.
Which time is healthier for us: summer time or winter time?
From the perspective of chronobiology, it would be more beneficial to remain on standard time, commonly referred to as winter time. This is the time that is more closely aligned with the natural solar rhythm.
I understand why we enjoy long, bright summer evenings. However, keeping summer time all year round would result in very late sunrises during winter. We would begin our days in darkness, while morning light plays a crucial role in regulating our biological clock.
Importantly, switching to winter time does not mean that the day becomes shorter. Day length changes naturally throughout the seasons. We merely redistribute the available daylight across our daily activities.
How can we prepare our bodies for the time change?
Experts recommend gradually adjusting sleep schedules, particularly before the spring time change. The autumn transition, when the clocks are turned back, is generally easier to accept because it gives us the opportunity to enjoy a longer night's sleep.
However, there is one important thing to remember: by switching to winter time, we are actually returning to our standard time zone, one that is more closely aligned with the natural solar rhythm. Although the term “winter time” may have negative connotations, from a biological perspective it is this time that is more compatible with the way our bodies function.
This coming Sunday, we are therefore about to embark on a small journey through time. By turning our clocks back, we will symbolically return to the rhythm according to which our ancestors lived and worked. And although time travel remains largely the subject of scientific speculation, this is one journey we can make without even leaving our beds. Better still, we will gain an extra hour of sleep ;).
Source: Prof. dr hab. Edyta Reszka, Department of Biophysics of Environmental Pollution, University of Lodz
Edit: Kacper Szczepaniak, Centre for Brand Communications, University of Lodz
