A new study published in the journal Chronobiology International reveals that doing so could lead to a dependency on artificial light to start activity.

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One hour back or one hour forward may seem insignificant in the grand scheme of things but the reality is that this twice-yearly reset isn't so easy on our internal clocks. Daylight saving time will end on November 7 this year, and people across the country (and in many other countries) will turn their clocks back one hour; this means the days will get shorter and the sun will set earlier until next spring, when the clocks jump forward and one hour of sleep is lost again. It only happens twice a year, but its disruption of the circadian rhythm has led many to call for the cancellation of daylight saving altogether. However, a new study published in the journal Chronobiology International reveals this could be bad for your health during the winter months. 

Researchers have studied the sleep impact of daylight saving time in the days and weeks after changing the clocks. They've found that the practice of springing ahead disrupts sleep cycles for at least a week and the number of car accidents historically rises after people reset their clocks. José María Martín-Olalla from the University of Seville is the first to explore what would happen if the event was canceled entirely. In his study, Martín-Olalla compared the daily rhythms of labor and the daily rhythms of sleep among people in the United Kingdom and Germany. 

woman waking up early morning stretching in bed
Credit: Diego Cervo / EyeEm / Getty Images

He chose those two countries because the U.K. has been using daylight savings since 1918, while Germany stopped the clock resetting practice between the end of World War II and 1980. The comparison shows that people in the U.K start their day exactly in time with the winter sunrise, while Germany starts its day 30 minutes earlier. Martín-Olalla believes that cancelling daylight saving time would lead to more human activity early in the morning. He notes this can be dangerous from a physiological point of view, largely because this will cause people to rely more on artificial light to wake up. 

Among other social factors and preferences, Martín-Olalla notes that the continued practice of daylight saving time in the U.K. has helped its residents to maintain alignment. In Germany, the 30-year absence of the practice has helped move human activity to earlier in the day. Martín-Olalla explains that this factor should be taken into account when weighing the risks of daylight saving time. The British are exposed to a change of time and its risks for two days of the year, while Germans have faced starting their day in the dark morning hours for three months of the year. 

The study author concludes the same results were found when American daily rhythms were tested against German daily rhythms. He notes that the U.S. population would be willing to start their work day earlier during the spring and summer months—when the sun rises earlier. However, rising before the sun in winter months comes with its only health risks. Overall, Martín-Olalla concludes that so long as society sets its schedules to a specific time of day rather than when the sun rises, both keeping and canceling daylight savings will come with its own health risks.

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