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U.Va. researchers explain adverse effects of daylight saving time on the body’s internal clock

Researchers in the University’s Biology department explain how daylight saving disrupts circadian rhythms

Although frequently attributed to Benjamin Franklin, daylight saving was actually adopted by the U.S. in 1918 so that natural light could be used later in the industrial day, ostensibly to conserve fuel during World War I. 

Assoc. Biology Prof. Ali Güler, who researches misalignment of our bodies’ clocks, said that daylight saving time is motivated solely by industry, without a basis in biology. 

“The natural sunset and sunrise is what you have evolved as a human for thousands of years,” Güler said. “That is the healthiest for your life.”

Daylight saving is a conventional — not a natural — shift. First-year College student Ploi Sripoom is from Thailand, a country that does not observe daylight saving time. 

She was intrigued by the phenomenon the first time she experienced it.

“It's pretty cool that you move the time forward, and then move the time backward,” Sripoom said. “But now I feel like it has complicated my life more than [benefitting it].”

Daylight saving time interferes with the precisely timed cycles of slightly longer than 24 hours called circadian rhythms on which our bodies operate. Our sleep-wake cycles, hormonal cycles and temperature cycles are all circadian rhythms. Daylight saving time forces our bodies out of these natural cycles.

In its healthiest and most natural state, a person’s body aligns itself with the cycle of the sun. Because our circadian rhythms are slightly longer than the astronomical day, they must be resynchronized every morning by light detected in the eyes. Light is detected by the photoreceptors rods and cones, which allow us to see, but also by the photopigment melanopsin, which detects light for purposes other than vision, especially for adjusting the biological clock.

Biology Prof. Ignacio Provencio discovered melanopsin in 1998, and his current research explores the impacts of the neurons containing melanopsin, which are known as intrinsically photosensitive retinal ganglion cells, or ipRGCs.

This light information is sent to a small brain region in the hypothalamus called the suprachiasmatic nucleus, or SCN, the body’s primary clock. Almost every cell in the body has its own biological clock, but the suprachiasmatic nucleus is, in Provencio’s words, “like a conductor of a symphony that ensures that [each cell] is playing in synchrony.” 

The 2017 Nobel Prize in Physiology was awarded to Jeffery Hall, Michael Rosbash and Michael Young for identifying some of the genes underlying this master clock. These three researchers are former members of the National Science Foundation’s Center for Biological Timing, an international hub of circadian research headquartered at the University from 1991 to 2002.

In addition to light, other cues that help reset the body’s clock are food, exercise and social interactions. If these cues are received by the body at unnatural times, this can result in circadian misalignment. Güler’s research focuses on the relationship between these cues and circadian misalignment.

Staying up too late produces short-term effects of circadian misalignment such as disorientation and cognitive difficulty, but long-term circadian misalignment can have more dangerous adverse effects. According to Güler, studies have shown that people who work the night shift are predisposed to cancer, cardiovascular disease and metabolic diseases like diabetes.

Both Güler and Provencio emphasized that our society is chronically misaligned. Our clocks have been screwed up ever since we screwed in the first light bulb, which first allowed us to do things at night – out of sync with our natural rhythms. The problem has been exacerbated by the rise of digital technologies.

“Everybody around the world tries to steal from their sleep as much as they can so that they can do stuff,” Güler said. “Or even inadvertently, you might be [misaligning your clock] by looking at your iPad or iPhone at night … You cannot tell your body that this light is not the same light as sunrise. The light is still activating the part of your brain that thinks it's daytime.”

Our society’s mindset towards sleep also harms our circadian rhythms.

“We as a society look positively among people who sleep deprive themselves,” Provencio said. “Like, ‘Wow, that person only needed four hours’ sleep.’ That's nonsense. That person needs eight hours’ sleep and they're barely surviving on four hours’ sleep … That's just not natural. I think we as a society have to recalibrate how we think about sleep.”

To demonstrate the magnitude of our circadian misalignment, Provencio cited the fact that the point of mid-sleep before the lightbulb was around midnight. Today, it’s closer to 4 a.m.

“We've already screwed up our clock,” Provencio said. “And then we further exacerbated that by adding daylight savings time. So we add another hour of error onto that.”

Standard time is not perfect. Noon shifts throughout the year due to the earth’s axial tilt. However, daylight saving time artificially shifts noon an entire hour away from what is perceived as natural to our bodies.

“I am a [night] owl,” Provencio said. “So emotionally, I love daylight savings because I get light in the evening, but intellectually I just can't justify the hour shift.”

Daylight saving time has been compared to shifting time zones, for example, the hour difference between central time in Chicago to eastern time in Charlottesville. In reality, Güler pointed out that the daylight saving time shift is much harder, because one’s body is forced to change its clock without the change in sunrise and sunset times brought by time zone changes.

“When you travel from Chicago to Charlottesville, what's happening is that the noon time is changing,” Güler said. “In daylight savings time … the information that is coming in is not changing.” 

Sripoom made a similar observation from her experiences adjusting to a new time zone.

“When I moved back to Thailand, what really helped my body adjust is the natural sunlight, but when you do daylight savings time, the amount of sunlight you get is still pretty much the same,” Sripoom said.

The switch to daylight saving time has observable harmful effects even besides the struggle to shift our bodies’ clocks. More heart attacks occur immediately after both the spring and autumn shifts. It is estimated that the spring shift is responsible for approximately 28 fatal traffic accidents per year.

Despite the scientific arguments against it, Americans still have to find ways to cope with daylight saving time.

“I would just throw away my alarm clock and just live my way,” Güler said. “That's one approach. But if you have to do things in the outside-world time, then you should be trying to get as many cues as possible that fit that new time zone … You need to eat, exercise and sleep at the right time.”

Provencio suggested going for a walk outside first thing in the morning if it’s light out. If it’s still dark, Güler recommended reading on an iPad or other electronics. The light from screens resets one’s clock in a similar manner to daylight, activating the melanopsin-containing neurons found by Provencio. Preemptively shifting one’s eating and sleeping schedule to the new time over five days, by 15 minutes a day, would also make the shift to daylight saving time easier.

“It will be hard no matter what you do,” Güler said. “It is not natural. I'll say it again. Daylight saving time is evil.”


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