How Turning the Clocks Back affects Our Circadian Rhythms

changing clocks causes sleep disruption

How Turning the Clocks Back affects Our Circadian Rhythms

We have all been there: the dreaded day in the spring where we turn the clocks ahead and lose an hour of sleep, and the welcome day in autumn where we turn them back and get an extra hour to snooze. Welcome to daylight saving time (DST).  According to American Academy of Sleep Disorder (AASM) President Dr. Ilene Rosen, DST is, essentially, a socially-imposed jet lag.


What are circadian rhythms?

Circadian rhythms are physical, mental, and behavioral changes that correspond to the lightness and darkness in an organism’s environment and generally follow a 24-hour cycle. In other words, these rhythms are our internal clock. This circadian clock has been widely observed in plants and animals, and, in 2017, Jeffrey C. Hall, Michael Rosbash, and Michael W. Young received the Nobel Prize in Physiology or Medicine for their discovery of particular molecular mechanisms which control the circadian rhythm in humans, too.

In humans, circadian rhythms are regulated by the suprachiasmatic nucleus (SCN) in the hypothalamus that, essentially, controls our sleepiness and wakefulness at regular intervals.

Despite this cycle’s biological inherency, outside factors can—and frequently do—have an impact. Lightness and darkness, in particular, affect circadian rhythms. For example, when it’s dark at night, our eyes signal our brain to release melatonin so we can fall asleep. This explains why our circadian rhythms largely coincide with day and night and why those who work graveyard shift find it so difficult to stay awake all night and sleep during the day.


Regular Sleep enables Optimum Circadian Rhythm

Regular sleep habits—such as going to bed and rising the same time every day—have been repeatedly shown to ensure an optimum circadian rhythm. Conversely, interruptions to our natural sleep cycles—such as daylight savings time—can disrupt these rhythms and wreak havoc on our bodies.

Circadian rhythms are also responsible for body temperature and various hormonal changes. For example, one’s body temperature dips during sleep and begins to rise during the last few hours of sleep in order to promote a sense of alertness in the morning.


Our sleep rhythms take weeks to recover properly

Ample research demonstrates that circadian rhythms change in four-minute increments which is the amount of time it takes for the sun to cross one longitudinal line. Makes sense, right? As the sun moves across the sky—which, in fact, is the Earth’s daily rotation—our internal body clocks adjust so that we are ready to sleep at night. With the socially created time change, our internal clocks neither recognize nor adapt, thus resulting in a disruption in these critical rhythms.

Whereas we might have been happily plodding along with our predictable appetite, arousal, alertness, sleepiness, and any of the other myriad subtle biological processes experienced daily, the seemingly simple act of setting our clocks ahead or back actually result in a self-imposed organic chaos that takes weeks from which to fully recover. That is, until the next time.


Reduction in brain cell production

This chaos has been oft studied. In one study of lab rats, after artificial alteration of the light-dark schedule, researchers noticed a 50 percent reduction in the growth of new brain cells, thus causing significant learning and memory problems that lasted as long as one month after the imposed “jet lag” ended. Similarly, a study of female flight attendants who worked for an airline that did not facilitate adequate jet lag recovery after traveling in different time zones uncovered substantial learning and memory deficits as well.


So, what next?

Proponents of maintaining the annual cycle changing the clocks cite that the increased use of artificial lighting has already harmed humans’ internal clocks to the point where a mere hour change twice a year is rather moot. Nevertheless, a growing body of research proving the ill effects of moving the clocks ahead or back on human health invalidates this argument. The bottom line is that the time changes of our current Daylight Saving Time process does, in fact, impact our circadian rhythms and, ultimately, our overall health, and thus we should look to having one standard time all year round as an affective prescription.

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