Researchers ask the basis of modern criticism

What is the best time to start the day given the variation in when the sun rises? This is the problem analyzed by Jorge Mira Pérez and José María Martín-Oola, teachers at the University of Santiago de Compostela (USC) and the University of Sevilla (US), in a study that has just been that has just been published in the diary Royal Society Open Science. In it they analyze the physiological and social foundations of the practice of seasonal change in time and assess their impact on health.

The study takes the cities of Bogotá and New York, which are on the same meridian, but on different widths, to point out that the sunrise in the winter is delayed by an hour and a half in the last city. “This slows down life in New York in the winter, but in the spring the delay in sunrise has disappeared and the activity can start earlier. Bringing the bells forward in the spring facilitates this adjustment,” says Mira.

The study includes various current and earlier examples of societies with delayed activity in the winter and earlier activity in the summer, in line with the synchronizing role of morning light for our body. “Modern societies have different synchronization mechanisms. For example, the use of a standard time in a large area, or the use of pre-set schedules. Time shift is another synchronization mechanism, which adapts human activity to the corresponding season,” says Martín-Ella. The authors suggest that the first weekend in April and the first weekend of October would be the most suitable time for the clocks to change.

The study assesses the impact of the seasonal change on human health, taking into account two types of effects: that associated with the change itself, and associated with the period in which daylight -saving time is in force. In the first case, the authors point out that published studies have not analyzed the problem Epidemiologically and that the evidence suggests that the impact is very weak.

“A very extensive study in the United States reports an increase of 5% in traffic accidents in the week after the clocks in the spring, but looks at that from one year to the next, weekly traffic accidents fluctuating by 15%. Changing the clocks has an impact, but it is very weak compared to the other factors that brand.”

“Changing the clocks has worked for a hundred years without a serious disruption. The problem is that in recent years it has only been associated with energy saving, while it is in fact a natural adaptation mechanism,” says Martín-Oolalla.

In the second case, the authors point out that the current controversy comes from an incorrect interpretation of the seasonal change. According to Martín-Ollalla and Mira, changing the clocks is not a time zone jump, nor does it ensure that the population is adjusted to the sun in a different location, nor does it ensure that their rhythm of life is misunderstood compared to the sun.

“In a sense, it is the other way around, changing the bells line out the start of the activity with the sunrise,” Mira notes. “In 1810 the Spanish national meeting had already made this kind of seasonal adjustment and there were no time zones or something like that. Social life is simply reorganized because the length of the day in the summer makes it possible to do things in the morning rather than in the winter,” says Martín-Oolalla.

Mira and Martin-Olalla are very critical of studies that report long-term effects of seasonal time change and associate them with an increased risk of cancer, sleep loss, obesity, etc. They point out that these studies analyze data in the same time zone in the US or Russia.

“They study what happens in New York and Detroit, for example, at the utmost of the US East Coast Time Zone, but on the basis of annual cumulative incidents. The time difference between the two cities is always the same all year round.

The study concludes by analyzing why changing the clocks in the 20th century was successful and with which difficulties medical associations are now confronted if they try to eliminate practice and use permanent winter time. They point out that the most important effect of the measure was to increase daylight hours during the leisure segment in the spring and summer.

“People agreed that they would go to work earlier in the spring and summer if it meant that they could leave earlier and enjoy the evening more by walking, going to the park or the beach – it seems clear, but it has to be said,” says Mira.

The elimination of changing the clocks, on the other hand, is confronted with a difficult dilemma when it comes to choosing what time to keep: to bring the start time forward in the winter, when the sun rises, or to return the start time in the summer, when the sun rises the earliest. “Both choice plays against human physiology, and that is why the termination of clock changes in both Europe and in America has proven to be difficult,” says Martín-Oolalla.

Mira says: “They have opened the box of a Pandora, they have worsened criticism of a natural practice that works reasonably well and now fear that the remedy is worse than the disease.”