Why changing the clocks twice a year is bad for your health – The Irish Times

Are you sleeping better since the clocks changed last week? According to science, this is how it should be. And you may notice that your productivity increases as your body adjusts to the winter circadian rhythm.

We just returned to permanent standard time, having spent the spring and summer months on daylight saving time (DST). The first time such time savings were realized was during the First World War. During World War II, Great Britain even introduced double time savings (setting the clocks by two hours). The proposal was that additional light in the afternoon would save energy by reducing the need for electric lighting. This idea has since proven inaccurate as heating needs may increase. Clock changes pose a challenge to our circadian health.

Our main body clock is located in a part of the brain called the hypothalamus. Although all tissues and organs in the body have their own clocks (called peripheral clocks), the brain’s master clock synchronizes peripheral clocks to ensure our organs work together harmoniously. But twice a year, this rhythm is disrupted when time changes, meaning that the master clock and all the peripheral clocks become out of sync—the master clock moves faster than the peripheral clocks.

Our body clock follows a circadian rhythm around which the day (roughly) revolves (dies). The circadian rhythm is an internal clock that causes the brain to switch between periods of wakefulness and sleepiness. Circadian rhythms include various elements that influence these intervals, including eating habits, body temperature and sleep duration, as well as external factors such as darkness and light.

From a health perspective, evidence suggests that daylight saving time in the spring is harmful. Scientists from the United States and Scandinavia used the electronic health records of hundreds of millions of people in the United States and Sweden to measure the health effects associated with daylight saving time. In a 2020 report published in the journal PLoS Computational Biology, they confirmed a significant increase in traffic fatalities (up to 30 percent on the day of daylight saving time), a short-term increase in workplace injuries (5.7 percent after spring time). shift, as employees sleep on average 40 minutes less) and increased rates of acute heart attacks (by about 4 percent).

( Summer time: clock hands are harmfulOpens in a new window )

In a recently published consensus position statement on clock changes, the British Sleep Society (BSS) said that we “should abolish biannual clock changes to prevent acute adverse effects on sleep, health, performance and safety.”

The statement, which has the support of the Irish Sleep Society, further urges the reintroduction of permanent standard time. “This option is preferable to switching to daylight saving time twice a year and is strongly preferable to permanent switching to daylight saving time,” it said.

Why is moving the clock forward worse for our health than moving it back? The shift to later morning light in the spring interferes with its valuable role in establishing the body’s natural rhythms. Meanwhile, exposure to light in the late afternoon delays the brain’s release of melatonin, a hormone that causes sleepiness. As BSS notes, this causes us to sleep less overall.

“Significant exposure to light before bed makes it difficult to fall asleep due to circadian mechanisms, as well as direct suppression of the sleep-promoting hormone melatonin and the direct preventative effects of light. Consequently, the additional delay in already late summer sunsets caused by daylight saving time (relative to bedtime) makes it difficult to get a full night’s sleep in summer… Taken together, seasonal daylight saving time, with its twice-yearly clock changes, is likely suboptimal for sleep and circadian physiology with potential risks to health and performance.”

Personally, I like daylight saving time. It’s great to have more time to spend outdoors. And while the scientific evidence is against permanent daylight saving time, it’s long past time for us to finally move away from changing the clocks twice a year.

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