Falling Back: Change Clocks on Sunday when Daylight Saving Time Ends

Daylight saving time comes to an end Sunday, November 5, so before turning out the lights Saturday night, remember to set your clock back one hour.

Theresa Lee, dean of UT’s College of Arts and Sciences and professor of psychology, said the one-hour shift will be easy to make but it may take a day or two to adjust.

“We are tuned to the daylight hours now, but be aware that in the evening it will be dark earlier, and for the next day or two your brain is adjusting to the delay,” Lee said. “You will be signaled to go to bed when you don’t need to, and you may be getting tired earlier than normal. These signals could make you sleepy on your drive home in the evening, so be aware and take a cat nap if you can.”

The signals Lee refers to are our circadian rhythms, which control our 24-hour internal clock and biological rhythms.

For thousands of years, people recognized the existence of circadian rhythms from observing nature. When the sun rises, plants open. When the sun sets, plants close. In the 17th century, however, researchers took plants from their native environment and placed them in lightless chambers. The plants still opened and closed on a nearly 24-hour schedule, which prompted a realization that the sun is not necessarily what drives the change.

So if it is not the sun, what drives the change in our biological rhythms?

“Genes,” Lee said. “The internal mechanisms that govern our circadian and biological rhythms are linked directly to our genes. Every organism has genes that control these internal systems. Two genes alternate like a see-saw. When one goes up, the other goes down. As the organisms get more complex, so do the factors that control our internal circadian rhythms. The role of light exposure is to synchronize our nearly 24-hour internal rhythms to a precise 24-hour external world.”

This year, circadian rhythms gained international attention when the scientists who first discovered the genes received the Nobel Prize in Physiology or Medicine. Jeffrey C. Hall, Michael Rosbash, and Michael Young used fruit flies to isolate the gene that controls the daily biological rhythm. The discovery laid the foundation for researchers to understand how our internal clock regulates not only our sleep cycle but also critical functions such as behavior, hormone levels, body temperature, and metabolism.

The work that garnered the Nobel Prize is featured in this NPR story.

More about Theresa Lee’s research is available in this Quest story.

CONTACT:

Amanda Womac (865-974-2992, awomac1@utk.edu)

Lola Alapo (865-974-3993, lalapo@utk.edu)