Circadian rhythm basics in 20 links

Have you ever tried waking up without an alarm clock? Unless you’re sleep depived, you’ll probably still rise with the sun…


Sunset and sunrise hold major influence over our sleep-wake cycles

SHC is courting the subject of circadian rhythms for the month of March. It’s a month when we have two shared events which influence our light-dark cycles in some way: the change to Daylight Saving Time and the vernal equinox (better known as the First Day of Spring).

There’s much to learn about this topic, but we have a whole month to do it! For today, SHC offers 20 links pointing to news involving the human circadian system: research, biology, disorders, therapies, comorbid conditions, and social impacts.

1. The Light/Dark Cycle

All living organisms (including plants) keep to a rhythm that is in tune with the light-dark cycles of the planet Earth. This rhythm is, for human beings, known as the circadian rhythm.

OCT 16, 2016 || MedicalXpress
Chronobiology—internal clocks in synch
“‘We’ve found that the other circadian clocks remain synchronized even without the master clock in the SCN,” Eichele explains – at least under the condition that light and dark alternate in a 24-hour rhythm.'”

2. Chronotypes

You might think you’re a morning person or a night owl, but what about lions or bears?

DEC 30,2016 || Sleep Review
Getting in Touch With Your Chronotype (podcast)
Dr. Michael Breus: ” One of the things I realized talking with my patients is that there were a lot of people who had real difficulty with their chronorhythms. Historically I had learned about chronorhythms and that there were morning people and evening people, then over the course of time it appeared there was some research looking at people kind of in the middle.”

3. Body clocks

It might surprise you to learn that the body has more than one body clock… in fact, it has many.

FEB 28 || Newswise
Watching the Clock: Biologist Katja Lamia Investigates Circadian Rhythms
Dr.Katja Lamia: “What you might not realize is that these circadian clocks control many other aspects of physiology,” said Lamia. “There’s even a clock in your liver that regulates the production and secretion of glucose depending on the time of day.”

4. Daylight Saving Time

Who knew this problematic time “adjustment” would have such wide-ranging repercussions?

FEB 22 || The Guardian
Spaniards’ lack of sleep isn’t a cultural thing—they’re in the wrong time zone
“A Franco-era decision to adhere to Central European Time may be to blame for everything from accidents at work to a low birthrate. But that could change.”

5. Circadian science

Our circadian system does more than guide us to wake up or fall asleep. It also assists in regulating many other aspects of human biology, including mood.

NOV 14, 2016 || Science Daily
How internal circadian clocks in neurons encode external daily rhythms of excitability
“Researchers have identified a key mechanism linking the master molecular clock in the brain to changes in the external firing activity of those circadian clock neurons. It involves the GSK3 kinase enzyme, which is also the target of mood-stabilizing drugs used to treat bipolar disorder.”

6. Zeitgebers

Zeitgebers translates into time cues and refers to the various environmental triggers that help direct our circadian rhythms, which mostly revolve around changes in light and metabolism following meals.

SEPT 14, 2016  || Five Thirty Eight
Sunlight And An Internal Switch Dictate When We Sleep
“This sun-sleep connection in humans and flies alike got scientists like Russell Foster, a professor at Oxford University in the United Kingdom, asking questions such as: What happens when we don’t have the mechanisms in our eye to distinguish dawn from dusk and send that message to the brain? Why can we still fall asleep according to the circadian rhythm? The answer, Foster said, is that mammals have a third layer of photoreceptors in the eye.”

7. Circadian Rhythm Sleep Disorders

While many are rare, some are quite common, and everyone has probably experienced at least a temporary circadian rhythm setback more popularly known as “jet lag.”

AUG 9, 2016 ||
What Are Circadian Rhythm Sleep Disorders?
“Circadian means ‘roughly daily.’ The word was coined some 50 years ago from the Latin terms circa, about, and diem, day. Circadian rhythms cycle daily according to the 24-hour rotation of the earth, and they are internally produced in all living things.”

8. Seasonal Affective Disorder

You don’t have to live in the far north to suffer from this circadian-related disorder.

JAN 17 || Loyola Maroon
Seasonal Depression in America
“Varela identified melatonin as a hormone that plays a huge role in the body’s circadian rhythm… The [circadian rhythms] can be disrupted by different external factors, such as the amount of light to which someone is exposed. When there is less light than usual, melatonin is produced at a higher rate.”

9. Jet Lag

People who travel transcontinentally on a regular basis know first-hand the challenges of managing sleepiness and wakefulness when they’ve gone off their normal routine.

SEPT 18, 2015 ||
Adventures in Time Zones – Handling Jet Lag
“One of the most popular questions I get about my book Travel Balance is around how to handle jet lag. Here is an excerpt from Chapter 5 on Adventures in Time Zones…enjoy!”

10. Shift work concerns

For more on shift work, check out our recent curation on shift work’s risk factors while on the job from last January.

FEB 23 ||
Healthy sleep and shift work
“BROOKINGS—Fifteen million Americans work outside the hours of 7 a.m. to 6 p.m. or work swing shifts rotating between day, evening or night shifts.”

11. Circadian disruption and cancer

Much of circadian rhythm research these days centers on the relationship between dysregulated rhythms and the development and treatment of various kinds of cancers.

FEB 24 || American Journal of Pharmacy Benefits
Circadian Rhythm Disruption Influence Cancer Development
“Tumor growth can be fueled by sleep disruption.”

12. Immune system links

The circadian rhythms have a felt impact in all areas of the body.

JAN 4 || HealthDay
Immune System Reboots During Sleep
“Study found levels of T-cells dropped three hours after falling asleep, came back up later.”

13. The metabolic body clock

Another major system driven by circadian rhythms is the digestive system and it doesn’t maintain a good balance if meals are unhealthy and timed poorly.

DEC 28, 2016 || Medical Daily
Poor Eating And Sleeping Habits: Unhealthy Foods And Inadequate Sleep Affect Everything From Hormones To Energy
“What happens if you have unhealthy eating and sleeping habits, such as staying up all night and sleeping during the day?”

14. Teens and late nights

More compelling evidence of the need to start middle- and high-school classes later?

FEB 27 || Medical News Daily
Tired teens 4.5 times more likely to commit crimes as adults
“Teenagers who self-report feeling drowsy mid-afternoon also tend to exhibit more anti-social behavior such as lying, cheating, stealing and fighting. Now, research from the University of Pennsylvania and the University of York, in the United Kingdom, shows that those same teens are 4.5 times more likely to commit violent crimes a decade and a half later.”

15. Aging and the Elderly

Our rhythms change as we grow older, leaving us with new challenges to living that are linked to circadian balance.

FEB 24 || Cosmos Magazine
Body clock genes may protect against ageing
“Night-work and disrupted sleep cycles may influence how you age.”

16. Curse of the lightbulb?

Blue spectrum light is not exactly off the hook, but research shows our sleeplessness may not be entirely blamed on modern living’s bad habits.

FEB 20 || American Sleep Association
It’s Not Just Pre-Bed Screen Time that Causes Sleep Loss
“Historical data suggests humans have been struggling to get a good amount of sleep long before the invention of electronic devices.”

17. Caffeine

Whether it’s high-powered cancer medications or more common stimulants like coffee or tea deliver, many consumed substances have a maximized metabolic effect based partly on circadian rhythm patterns.

FEB 17 || New York Magazine
How to Time Your Coffee for Maximum Effectiveness
“According to a study published in November in the journal Frontiers in Psychology and recently highlighted by Mental Floss, coffee’s memory-boosting powers are at their most potent at a specific point during the day.”

18. Endogenous melatonin

Unlike the questionable stuff you buy at the drugstore, this is the stuff released by the pineal gland every night as part of our process of preparing for sleep. 

FEB 28 || Dr. Eddy MD
What Is the Pineal Gland?
“Structurally, the gland is mostly made up of cell bodies called pinealocytes, which produce melatonin.”

19. Resetting your rhythms

I can personally vouch for this solution for wonky sleep-wake rhythms, but unfortunately, it’s the dead of winter, when most people aren’t likely to partake in this experiment, for all practical purposes.

FEB 2 || Science Alert
Can’t Sleep? a Weekend of Camping Could Reset Your Circadian Rhythm, Study Suggests
“An even bigger difference was seen when the researchers sent five people camping for a week during the winter solstice—the extra time in the outdoors resulted in melatonin being released in their bodies 2.6 hours earlier than before the experiment.”

20. Light therapy (also known as phototherapy)

We can’t truly think about circadian rhythm disorders only as sleep disorders, as they can also lead to disorders of wakefulness.

FEB 23 || Sleep Resolutions
Using light therapy to stay awake during the day
“Light therapy, also known as phototherapy, is purposeful exposure to artificial light. It’s meant to simulate the effects of being exposed to direct and natural sunlight.”

About Tamara Kaye Sellman (621 Articles)

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