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Why “Springing Ahead” Our Clocks Messes With Our Bodies

A woman in bed, stretching as the morning sun glows on her.

Bring up daylight saving time and you’re bound to hear a variety of responses. The process of setting our clocks forward or backward twice a year can certainly throw our bodies for a loop, but the effects on the body can be greater than what many of us understand. Sleep is vitally important, and even minor disruptions can cause issues.

Daylight saving time was permanently established in the United States in 1966 by the Uniform Time Act, but states have always had the choice to opt out with the passage of a state law. Currently, Hawaii and Arizona are the only states that do not participate, but that could change soon.

This session, the Texas Legislature is considering a bill that would eliminate daylight saving time in Texas.

To understand more about changing the clock and how even that minor change can affect our bodies, we talked to Art Markman, a professor of psychology at The University of Texas at Austin, about the psychological effects.

Q. What are circadian rhythms, and why are they important?

Art Markman:
Many functions of the body are synchronized to the day-night cycle. These functions are called circadian rhythms. The sleep-wake cycle is one of those rhythms. Another is the cycle of kidney function. When you are asleep, your kidneys produce less urine, so that you can sleep for an extended period of time without having to wake up. These rhythms adjust at different rates. The rhythm controlling the sleep-wake cycle changes faster than the rhythm associated with kidney function. That is one reason why people who travel long distances (like from the U.S. to Europe) will still wake up at night for several days after they are able to fall asleep at the bedtime hour.

Q. Who is most affected by a disturbance in circadian rhythms?

AM: Everyone is affected by disturbances in circadian rhythms. However, lack of sleep has its biggest short-term effects on children and young adults. The day following a night of bad sleep has a significant impact on these individuals in their ability to learn new information and to control their mood. Older adults are less affected in the short term by poor sleep. But, prolonged periods of bad sleep in adulthood is associated with cognitive deficits in old age.

Q. Why is the short-term sleep disruption from daylight savings a big deal?

AM: Any disruption in sleep habits leads people to sleep more poorly. It is hard to fall asleep an hour earlier than your habit, and so the spring time change causes people to be tired for several days after the change. Many people suffer from difficulties falling asleep or staying asleep because they do not have good sleep habits. The time changes associated with daylight saving are just one more disruption to already poor sleep routines.

Q. What are the arguments for and against daylight saving?

AM: The primary argument for daylight saving time is that it sets the time for sunrise around the time that people wake up so that they don’t sleep through a lot of the daylight. It puts that daylight later into the afternoon and evening when people are likely to be awake and active.

The primary argument against it is really an argument against time changes. In particular, springing ahead disrupts sleep in two significant ways. First, Saturday night leaves one fewer hour of sleep for people who have to be somewhere early on Sunday morning. Second, if someone typically goes to sleep at 10 p.m., their body will feel as though it is 9 p.m. on that first day, and so their sleep habits are being disrupted.

Q. Are there negative health implications associated with poor sleep?

AM: There are a number of negative health implications. Poor sleep habits can make it hard for people to regulate their mood, which can lead to high stress levels. Prolonged stress leads to reduced immune system function. Sleep also helps the brain to clear toxins and waste from respiration. Prolonged periods of poor sleep can also lead to the buildup of waste products in the brain.

Q. Any tips on how people can get better sleep?

AM: Create a regular routine and select a fixed bedtime. That bedtime may be early or late in the night depending on personal preference. Try to get to bed within 30 minutes of that bedtime each day.

And stop watching screens (television, video game, phone, tablet, computer) about 30 minutes before you plan to sleep. Try to engage in the same activities before bed so that your brain settles into a sleep mode.

Different people need different amounts of sleep. You may also find that your sleep needs change over time. As people get beyond middle age, they frequently find that they need less sleep than they did when they were younger.