2 posts tagged “circadian”

Circadian rhythms and health: What’s the connection?

Posted November 20th, 2017 by

More than 3,600 PatientsLikeme members are living with insomnia, and 100+ report a circadian rhythm disorder. In October, three researchers won the Nobel Prize for their work examining the relationship between sleep, circadian rhythms and health. So with Daylight Saving Time just behind us, we’re bringing you more info about the “body clock” and how it can affect health.

Let’s back up — what ARE circadian rhythms?

  • Circadian rhythms are physical, mental, or behavioral changes that follow a daily cycle. They’re regulated by biological clocks, which exist in most tissues and organs in the cells.
  • A master clock coordinates all of the biological clocks and contributes to our sleep patterns (it also affects eating habits, body temperature, and other functions).
  • These internal “body clocks” are affected by environmental cues, like sunlight and temperature.

New research making headlines

The 2017 Nobel Prize in Medicine was awarded to three Americans for their work on circadian rhythms. The Nobel committee said their research was pivotal, because “the misalignment between a person’s lifestyle and the rhythm dictated by an inner timekeeper — jet lag after a trans-Atlantic flight, for example — could affect well-being and over time could contribute to the risks for various diseases.”

What’s the relationship between sleep and circadian rhythms?

  • Circadian rhythms help determine our sleep patterns. The body’s master clock, or SCN, controls the production of melatonin, a hormone that makes you sleepy. It receives information about incoming light from the optic nerves. So when there is less light—like at night—the SCN tells the brain to make more melatonin so you get drowsy.
  • For most adults, the biggest dip in energy happens in the middle of the night (between 2:00am and 4:00am) and just after lunchtime (ever crave a post-lunch nap around 1:00pm to 3:00pm?).
  • When things disrupt your sleep habits, like jet lag, daylight savings time, or a late night, they also disrupt your circadian rhythms, which can leave you feeling more irritable and make it harder to concentrate.
  • People who work rotating or shift schedules (nurses, law enforcement, etc.) are most at risk for disrupted circadian rhythms. Having an irregular schedule can wreak havoc on circadian rhythms.
  • All caught up on sleep? You won’t feel the dips and rises of your circadian rhythms as strongly. When you’re sleep-deprived, you may notice bigger swings of sleepiness and alertness.

How can it impact health and chronic illness?

  • Circadian rhythms influence short term memory, creativity and learning performance, weight gain/loss and your immune system.
  • Lack of sleep affects levels of metabolic hormones that regulate satiety and hunger. When you’re sleep deprived, your body decreases production of leptin, the hormone that tells your brain you’re satisfied, and increases ghrelin, a hormone that triggers hunger.
  • Disrupted circadian rhythms and lack of sleep are associated with diabetes, depression, bipolar disorder and seasonal affective disorder — and can negatively affect many chronic illnesses, including Parkinson disease, Alzheimer’s, MS, gastrointestinal tract disorders and kidney disease.

Think your circadian rhythms might be out of whack?

  • Try minimizing your screen time with electronics that mimic daylight (laptops, TV’s, cell phones, portable game consoles, etc.). And if possible, try to maintain a regular schedule when it comes to sleep, wake and meal times.
  • If you’re having trouble sleeping, feeling tired often or noticing any other symptoms, talk to your doctor.

How are you sleeping? Join PatientsLikeMe to connect with and learn from nearly 3,600 members with insomnia and share how your condition affects your sleep and circadian rhythm in the forum.

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“We have become 24/7 creatures in a 24/7 society”: an interview on sleep with Fred W. Turek, Ph.D.

Posted May 20th, 2015 by

Dr. Fred Turek is Director of the Center for Sleep and Circadian Biology at Northwestern University. He holds a BS in biology from Michigan State University and a PhD in biology from Stanford University.

Dr.Turek’s current research focuses on the genetics of the circadian clock system, the effects of advanced age on behavioral and endocrine rhythms, the links between sleep, circadian rhythms and energy metabolism, and the role of melatonin in modulating sleep and circadian rhythms.

Said another way, he’s the expert on all things sleep-related.

Dr. Turek, during your lecture in Chicago about circadian rhythms and sleep, you talked about how modern life ‘battles’ ancient drives and Mother Nature. Could you explain more about that?
Yes, the ancient drives refer to the fact that we evolved on this planet for millions of years with one dominant feature of the environment: the relentless diurnal or 24-hour change in the light/ dark (LD) cycle, which is due to the rotation of the Earth on its axis.

This results in most of the Earth facing the sun and its light and warmth at one time of day, and later, that same part of the Earth is in dark and colder. Like all other living organisms, we evolved internal biological clocks, which have a period of “about” 24 hours (the internal clock has a circadian period that is about 23-25 hours in length). This internal clock is synchronized to the 24-hour external day night cycle, and until Edison came along about 125 years ago, the human internal clock was in lock step with the LD cycle. We were awake and active during the light/day and asleep and generally inactive during the dark/night.

However, over the last century, we have become 24/7 creatures in a 24/7 society, and we are often not paying attention to signals from our internal clock. Indeed, we are doing battle, if you will, with our internal 24-hour biological nature.

You’ve mentioned it was discovered that the daily rhythm of melatonin could influence other rhythms in animals. How has the research evolved since then?
I would say that research into the role of melatonin in regulating circadian rhythms, particularly in mammals, was slow, but has picked up speed over the last decade. While we still do not understand the overall function of the robust 24-hour melatonin rhythm (melatonin levels are low during the day and high during the night in all species, including humans), it appears to act as a mild hypnotic, at least in humans. Perhaps more importantly, it appears to act as a circadian organizer that links other 24-hour physiological and behavioral rhythms to one another.

In that Chicago lecture, you said, “When the clock stops ticking, metabolic syndrome explodes.” Can you share more about that?
That clever title came from Dr. Bart Staels in a short opinion piece he wrote for Nature soon after we published a paper in Science (2005). The paper demonstrated that animals carrying two copies of a mutated core molecular circadian gene (called Clock) can lead to the loss of all circadian rhythms, as well as increased weight and signs of the human metabolic syndrome: increased visceral obesity, insulin resistance and hypertension.

You make the point that, while the master circadian clock is located in the hypothalamus of the brain, 10-30% of the genes throughout the entire body are under circadian control. What does that mean in terms of how the “clock” affects health and disease?
Let me preface the answer to that question with a little background: Up until 10-15 years ago, researchers in the field thought a master circadian clock regulating all of our 24-hour rhythms was located in the hypothalamus, and that few other areas of the brain or peripheral tissues were capable of generating their own circadian rhythms.

With the discovery of many of the genes and their protein products that make up the molecular 24-hour clock came the surprising discovery that the molecular clock machinery was actually in all the cells, tissues and organs of the body. Equally surprising were recent discoveries indicating that this cellular circadian clock is regulating the timing over 24 hours of somewhere between 10-30% (and perhaps up to 50%) of all the expressed genes in a particular tissue or organ.

We call these genes “clock controlled genes.” What happens if that clock machinery breaks down, say in a disease state or with advanced age, in a particular tissue or organ? That is a question that we and many other laboratories are trying to answer right now. Humans, as in all animals, are not only spatially organized, we are also “temporally organized,” and a breakdown of that temporal organization, maybe only in a particular organ (lung, liver or pancreas, for example), could lead to disease in that particular tissue, even if all the other parts of the body have clocks running normally.

At one point in your lecture you went as far as to say, “I think insomnia is causing depression.” Could you elaborate on that?
I used such a direct statement since for years the importance of insomnia for causing or contributing to depression has been on the back burner of thinking in the field – with the dominant thinking being that depression causes insomnia. When I first wrote that statement, I was trying to be provocative, but in reality I believe it is likely that insomnia may be a contributing cause to at least some forms of depression, as well as perhaps increasing the severity of the symptoms of depression.

Many PatientsLikeMe members are living with conditions that may be impacted by sleep problems. Or on the flip side, their conditions might be impacting their sleep, right?
Absolutely: It is a two-way street. It is now clear that many, many mental and physical disorders are associated with poor sleep. Of course, there is the cause and effect or rather the chicken or the egg question: Which came first? In one sense, I am less interested in the answer to that question than I am in the question: If I treat poor sleep or insomnia in someone with a given condition, will I have a positive benefit for the treatment, prevention or even cure for the condition?

So, then, do you see a connection between the sleep we get and the conditions we live with?
Yes, PatientsLikeMe members should treat obtaining adequate sleep as a top priority in their lives – do not “cheat” on sleep. And if you are having trouble sleeping, perhaps due to your condition, tell your doctor about your sleep problem, and seek ways to remove that problem from your life.

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