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Is Daylight Saving Time Hazardous to Your Health?

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The Jaffa Clock Tower.
The Jaffa Clock Tower.Credit: Ofer Vaknin

Israel moved to daylight saving time at 2 A.M. Friday. Clocks moved forward one hour and most people will begin their daily routines an hour earlier starting Friday.

In 1916, Germany became the first country to introduce daylight saving time, in order to save energy on artificial lighting during World War I. DST, or summer time, is observed in many countries, but increasing evidence from numerous studies points to health risks associated with these annual time changes.

The immediate problem associated with the switch to DST is the loss of an hour’s sleep on the day of transition. This loss may seem negligible, but in the U.S. and Europe a dramatic spike in the number of deaths on the day after the change has been recorded – mainly due to heart attacks and traffic accidents, caused by sleep deprivation. However, the long-term risk of changing to DST comes from its impact on our biological clock.

This internal mechanism generates regular circadian fluctuations in a very large number of processes in the human body, a rhythm that is expressed in various physiological and biochemical processes, as well as in our sleep patterns. The biological clock is a genetic network composed of interactions between genes and proteins. Many cells in different tissues operate as timekeepers, but the master clock resides in the suprachiasmatic nucleus in the brain, located at the base of the hypothalamus. The human circadian rhythm is longer than 24 hours (it can be 25 hours), but under normal circumstances it receives cues from the environment, especially from the cycles of light and darkness, making it synchronize to exactly 24 hours.

Life in our modern age, especially under electric lighting, poses an immense challenge to our biological clock and its ability to synchronize with the daily cycle. Many people experience such synchronization difficulties after a trans-Atlantic flight that cause jet lag, which is associated with headaches, fatigue, sleep problems and other symptoms. Jet lag after a flight is not a health problem since the body’s clock synchronizes with the new light cycle within a few days. But jet lag that occurs constantly and often can lead to health problems. Studies done on flight attendants suffering from continuous jet lag have shown that they suffer from a significantly higher incidence of cancer, compared to the rest of the population.

The number of people who are exposed to chronic jet lag is huge, since anyone doing shift work (medical personnel, people in manufacturing jobs) are required to work in opposition to their biological clocks. Studies have shown that shift workers also have a significantly higher incidence of cancer and other diseases, compared to the general population.

The main cause of these higher rates of disease in shift workers is the exposure to artificial lighting at night. Such lighting delays the accumulation of the hormone melatonin, which is the main trigger for falling asleep. This causes delays in the process of falling asleep. Cumulative evidence gathered in many studies has brought the World Health Organization to declare artificial nighttime lighting as a cancer risk for shift workers.

In fact, most of us experience an interference with our biological clocks when we wake up in the morning using an alarm. Most schools and workplaces open at 8 A.M. In order to arrive on time, most students, staff members and employees need to wake up in an unnatural manner. Most of us live under a time regime that is imposed on us, suffering from socially induced jet lag.” This lag can be assessed by the gap between our wake-up time during the week and on weekends. If the gap is large (which is typical for “night owls,” who wake up later naturally), one suffers from significant socially induced jet lag, which could endanger your health.

The human body has to navigate its way through three different time regimes: the biological clock, the sun clock and the “social” clock. The more synchronized these clocks are, the less disease caused by a lack of synchronization. From this one can infer that moving our clocks twice a year, with the initiation and cessation of DST, hampers the biological clock’s ability to synchronize. The onset of DTS is particularly problematic, since it exposes us to exaggerated lighting at night and deprives us of the darkness required for natural sleep. During the application of DTS, we tend to go to sleep later, but we still have to get up at the same time in the morning in order to get to work. The result is an aggravated socially induced jet lag.

Over the last two years, position papers have been published by different scientific communities, including the American Academy of Sleep Medicine, the European Biological Rhythms Society and the Society for Research of Biological Rhythms in the U.S., calling for the abolition of DTS due to its serious health implications. Many states and regions around the world have decided to cancel its implementation, including Australia, Russia and most countries in Asia and Africa. The province of Ontario in Canada stopped using it this year. The European Parliament decided last year to do so in principle. It’s time for Israel to adopt a similar decision and keep one time that is closer to our body’s normal rhythm for the entire year.

Eran Tauber heads a research group studying biological clocks at the University of Haifa.

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