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Posts Tagged ‘circadian rhythms’

Winter, sleep and your circadian rhythms

January 19th, 2015 Raquel Rothe
American Academy of Sleep Medicine  |  Nov 13, 2014
Unlike animals, humans do not need to hibernate during the winter. It may feel like you need more sleep during the winter months because the days get shorter. However, your actual sleep need does not increase.

It is normal for sleep habits and activity cycles to change a bit as the seasons change, according to Dr. Emerson M. Wickwire, Sleep Medicine Program Director at Pulmonary Disease and Critical Care Associates in Columbia, Md., assistant professor at Johns Hopkins School of Medicine. If you experience excessive daytime sleepiness or fatigue or a noticeable change in your mood, irritability or ability to think or remember clearly, then you should talk to a board-certified sleep physician.

“The biggest mistake that people make when it comes to sleeping in winter is ignoring their body’s natural rhythm. Even if you’re tempted to stay in bed or on the couch all day long, unless you are sick it’s a good idea to get up and move around.”

Staying in bed or on the couch all day long when you’re not sick may throw off your circadian rhythms. The visual cues of light and darkness “set” this internal clock keeping it synchronized to a 24-hour cycle.

A number of sleep disorders that are linked to misaligned circadian rhythms including insomniajet lag andshift work disorder. Abnormal circadian rhythms have also been blamed for depression, bipolar disorder and seasonal affective disorder, which is more common in the winter.


  • Increase exposure to light
  • increase or maintain physical activity
  • Use a humidifier or nasal rinse to keep your airway passages from drying out
  • Make sure that your bedroom is not too warm or too cold

Circadian Rhythms in Modern Life

October 10th, 2013 Raquel Rothe
Circadian-RhythmThis paper discusses the Western human circadian rhythm and its relation to health.

1. The circadian rhythm of a modern man

“In 1910, the average American slept nine hours a night, disturbed only by the occasional Model T backfiring. We now average 7.5 and declining.” – Robert Sapolsky (Why Zebras Don’t Get Ulcers)

The typical Western person’s circadian rhythm differs in at least three main ways of which the human species has adapted to in its history

First of all, the amount of light during night time. Before artificial lighting popularized, people spent the night in almost complete darkness . Today, most families live in almost constant light even if it is pitch black outside.

Second, the amount of light during the day is now lower than it has ever been in human history . The reason is that we do not spend much time outdoors. We spend the days indoors, where the amount of light can be over a hundred times less than the amount of light outside.

“Bright light can help shift even the most extreme body clocks,” says Professor Roenneberg. “But the amount of light in most offices is laughable. You would be lucky to get 400 lux [a unit of measurement of the intensity of light] at a bright vertical office window during the day, whereas outside on a cloudy day in summer you would experience more like 10,000 lux. If it’s a blue sky, you could get as much as 150,000 lux.” (Independent: Could you be suffering from ‘social jet lag’?)

The third current problem is sleep duration, which has been decreasing in recent decades.

In a study on connections between sleep and obesity published this year, it was found that in the 1960’s people slept about 8-9 hours a night. By 1995, the amount had shrunk to seven hours. In 2005, a third of the population slept for about six hours a night. Actigraphic and polysomnographic studies show that middle-aged people only get six hours of sleep on average. (Reiter et al. 2011)

Now we are going to speculate the effect of these on health by studying some research material on the subject.

2. The circadian rhythms’ connection with health – shift work and clinical sleep studies

People doing shift work is an interesting group when reflecting on the circadian rhythms’ effects on health. These people must for follow a very unnatural sleep rhythm because of their profession. Epidemiologic data shows that certain health problems are much more common among shift workers than in the average population.

  • Obesity – In a Swedish study 27485 people answered a survey and according to the results, shift work correlates to a 40% higher risk for obesity (BMI over 30) after adjusting for age and socioeconomic factors. (Karlsson et al. 2001)
  • Breast cancer – In Denmark the risk of breast cancer in nurses is 80% higher in those working day and night shifts. The longer the shift work had lasted, the larger the risk was. Those who had been working in shifts for over two years, the risk was 160% higher (after adjusting the results) than in those only working during the day. (Hansen&Stevens 2011)
  • Cortisol and obesity – In the Netherlands a small study (122 persons) showed, that in people doing shift work the amount of cortisol in a hair sample was larger (47 .32 vs 29.72 pg/mg). In young people doing shift work the BMI of these people was clearly higher compared to day workers (27.2 vs 23.7). (Manenschijn et al. 2011)

“If light were a drug, the government would not approve it,” says Professor Charles Czeisler of the Harvard Medical School. And Professor George Brainard of Thomas Jefferson University in Philadelphia, adds: “Humans evolved on a planet without electric light over thousands and thousands of generations. The body is designed to be alert and awake during daytime hours and to sleep at night. Now we have a 24-7 society that isn’t in harmony with our biological design.”

“In the new study, scientists grafted human breast cancer tumours on to rats and infused them with blood taken from women during the day, in the early hours of the morning, and after being exposed to light at night. The blood taken in darkness slowed the growth of the cancers by 80 per cent, but the blood taken after exposure to light accelerated it.” (Independent: Avoid breast cancer. Sleep in the dark…)

If even a few years of shift work can clearly be seen as an elevated risk for breast cancer, could a lifetime of sleep deprivation or other light related problems that affect most people have an effect on the risk of chronic disease? I would say it’s possible.

Some experimental studies have been done, in which for example the test subjects duration of sleep has been reduced.

  • In a study conducted by the University of Chicago, eleven young men were sleep deprived (four hours of sleep per night) for six days. This caused the test subjects’ cortisol levels to rise and sugar tolerance to temporarily decline. (Spiegel et al. 1999)
  • The same university published a cross over study, in which 10 overweight people were calorie deprived for two different time periods. During the one period they were allowed to sleep for 8.5 hours and in the other only 5.5 hours. The actual amounts of sleep were 7h 25 min and 5h 14 min. In both groups the subjects weights declined 3 kilograms, but in the sleep deprived group 80% of this weight was muscle. Without sleep deprivation 52% of the dropped weight was muscle and the rest fat. (Nedeltcheva et al. 2010Whole Health Source – The Big Sleep)
  • In an American study conducted in 2009, ten test subjects followed a 28 hour day instead of the normal, 24 hour day. Half way in the study the test subjects spending night time as day time, the test subjects leptin levels were about 20% lower during the day than before the test but during sleep the difference was smaller. Also the insulin levels were on average 22% higher and after breakfast (2h) the blood sugar rose 32% higher than normally. (Scheer et al. 2009)

3. The environmental light and melatonin secretion

Next we’ll dive into the world of melatonin, but first the basics.

The ambient light contributes significantly to the body’s circadian rhythm. In particular, blue light (460-490nm) inhibits the pineal gland from secreting melatonin. Melatonin is often called the dark hormone, because it is secreted at night.

Only blue light affects the secretion of melatonin, so if a person is wearing blue blocker sunglasses, melatonin secretion will not be affected. Of course, removing the short wavelengths (blue light) from lamps will have the same effect. (Sasseville et al. 2006Kayumov et al. 2007Chellappa et al. 2011).

Even normal lighting before going to sleep can decrease melatonin secretion which can have effects on health. The melatonin blocking effects of blue light can be significant especially in winter time, when the small amount of daytime exposure to light can cause the body to react more significantly to bright artificial light used in the evening. (Gooley et al. 2011Higuchi et al. 2007Park&Tokura 1999).

Only blue wavelengths of light have effect on melatonin secretion, but for example cortisol levels can rise from other wavelengths as well. (Figueiro&Rea 2010Leproult et al. 2001).

Below are empirical studies in which the amount or type of light has been altered and the results have been documented:

  • In Ohio the effect of blue blocker glasses and their effect on a person’s quality of sleep and mood was studied. Orange colored blue blocking glasses improved quality of sleep, but grey control glasses didn’t. (Burkhart&Phelps 2009)
  • Blue blocker lenses seem to be very effective for insomnia in ADHD subjects. The average PSQI score fell from 11.15 to 4.54, dropping below the cut-off score of 5 for clinical insomnia“. (Fargason et al. 2013)
  • Doctor James Phelps described a small experiment in his article, in which persons (n=21) suffering from bipolar disorder and sleep complications were given blue blocker glasses for evening usage. Nine test subjects felt their condition improve “very much” while eight people didn’t notice any effect. Also a few felt smaller improvement and also a few were somewhat bothered because of falling asleep too early. (Phelps 2008 ; see also Seth Roberts’ blog post Bipolar Disorder: Good Results with Blue-Blocker Glasses).
  • In New York State a study was conducted in which school children wore blue blocker glasses (with orange lenses) during the day for one school week. This caused their melatonin secretion at evening to begin a half an hour later than normally. (Figueiro&Rea 2010)
  • Bright light treatment seems to be beneficial in the treatment of specific mood disorders, including depression and seasonal affective disorder (Golden et al. 2005Lieverse et al. 2011).

I believe that the effect seen in the bright light study mentioned before could be replicated and possibly surpassed with ordinary daylight. Expensive bright lights shine light at 10 000 lux at the best, but outside the amount of light can be ten times larger. Daylight might also have other benefits like vitamin D production caused by UV-radiation, the temporary lowering of blood pressure caused by nitric oxide metabolism, plus the stress-relieving effects of red and near-infrared light. The problem of course is, that in the winter time natural light isn’t available in large amounts in all parts of the world. (Holick et al. 2007Opländer et al. 2009Feelisch et al. 2010Barrett&Gonzalez-Lima 2013).
Melatonin can also be used as medication and in clinical trials it has been portrayed as quite a useful drug:

  • In one study, melatonin had quite a good effect on irritable bowel syndrome. (Lu et al. 2005)
  • Melatonin supplements might be beneficial to patients suffering from CFS and/or fibromyalgia. The benefits are possibly caused at least in part, by the improvement of subjects’ quality of sleep. Those who used melatonin showed significant improvement in sleep / sleep parameters. (Hussain et al. 2011van Heukelom et al. 2006)
  • According to a recent meta-analysis of melatonin, a slightly higher dose (20mg) seems to be have quite a large effect on conventional cancer treatments. It decreases the mortality rate and reduces treatment side effects significantly. (Wang et al. 2012, see also Mills et al. 2005)

Even though light is very important influence to human / animal circadian rhythm, apparently among light, food, other people and physical activity also have a notable effect. I’m not yet particularly familiar with that data, so it will not be discussed in this essay.

4. Tips for improving sleep and health
Get some light after waking up and during the day

The effect of light on the circadian rhythm seems to be the largest immediately after waking up, so walking outside for ten minutes after waking up can be beneficial.

If you want an adequate amount of blue light during the winter, there are roughly two types of light therapy lamps. Large ones and small ones. The larger lamps have a large lux amount (they are brighter), and the smaller ones compensate with the light spectrum and by a smaller distance between the user and lamp. The lights of small lamps are slightly bluer to compensate for the smaller intensity of light. (Meesters et al. 2011)

I have noticed that if I don’t get enough light during the first 1-2 hours after waking, I’ll stay more or less sleepy for the rest of the day.

Sufficient blue light during the day might be important for alertness, mood and sleep. (Viola et al. 2008)


A light box (left), blue blocker sunglasses (right).

Avoid unnecessary light during the late evening

Turning lamps off and dimming your computer’s display are some of the simplest non-pharmaceutical ways to increase melatonin levels at night. And to make it easier to fall asleep.

If I get a too much light into my eyes at bedtime, I will suddenly become very alert and that means that I need to wait another 1-2 hours until I’ll be able to fall asleep. When I was in high school, this was a significant problem for me. I had to wake up at 7am on almost every morning, yet I usually couldn’t fall asleep before midnight. The late evening, the time when I should have been already sleeping, was the most productive time of the day, because of the strong alerting effect of light at night.

F.lux is a popular computer program that changes the displays color to orangish automatically in the evening. Personally I prefer to use Gamma Panel (gapa.exe), a program that allows you to remove blue light completely from your computer screen.

The blue blocker sunglasses are another alternative. If you want to block out blue light, you can buy some nice lenses from ebay (use keyword “aviator blue blocker”) and wear them in the evenings.

Also red light bulbs (LED) can be used can be used as night reading lamps.

Poor curtains can leave the room too bright during the night or early morning. A sleep mask is an easy and cheap way to correct this problem.

redden computer screen

In the evening, I usually use Gamma Panel software to redden my computer screen. This makes falling asleep much easier.

Nutrition and sleep

A combination of melatonin, magnesium and zinc has been shown to have great results in sleep quality studies. (Rondanelli et al. 2011)

In a few studies, glycine has been shown to improve quality of sleep. The primary source of glycine is collagen protein or gelatin. This means that head cheese and bone broth are a good source of glycine and can improve quality of sleep. I occasionally make jelly out of gelatin and concentrated juice. (Yamadera et al. 2007Inagawa et al. 2006)

I personally agree with the basics of Matt’s “Eat for Heat” ideology. If I have trouble falling asleep, I try to eat some extra starch and fat calories (e.g. rye/wheat bread with butter and cheese) and avoid too large amounts of fluid.
Other ideas

Seth Roberts, a Professor of Psychology, has written a lot about his various experiments, some of which are related to circadian rhythm. (Roberts 2004Seth’s blogPerfect Health Diet – Seth Roberts and Circadian Therapy)

Here’s a list of things that, according to Roberts’ experiments, could benefit those having problems related to their diurnal rhythm.

  • Intake of vitamin D3 might affect one’s circadian rhythm if the doses are high enough. Because of this, Roberts has recommended taking 4000IU (100µg) of vitamin D shortly after waking up. (1,2,3,4,5,6,7,8,9,10,11,12,13,14,15)
  • Standing so much that your legs become fatigued might be useful. Roberts noticed consistently high quality of sleep when he stood at least 9 hours during a day. He also noticed that this time can be dramatically reduced by standing on one leg. (1 (p.13-15) ja2)
  • Morning Faces Therapy: According to Roberts, if one sees faces after waking up, he/she will be more sleepy and unmotivated in the evening, but more alert and motivated in the next morning. (1 ja 2 (p. 5-13)

A mirror, to see my own face during my piano improvisations. (Seth Roberts' faces therapy)

A mirror, to see my own face during my piano improvisations. (Seth Roberts’ faces therapy)


Thanks to Laura Mikkonen for doing most of the translating work.

Stay healthy when traveling abroad

August 1st, 2012 Raquel Rothe

Good article with resources for you to stay healthy as you travel:


Sleep Deprivation Effect on the Immune System Mirrors Physical Stress

July 30th, 2012 Raquel Rothe

Researchers Trail Twitter to Track World’s Mood Swings: Work, Sleep and Daylight Play Role

November 5th, 2011 Raquel Rothe

Researchers Trail Twitter to Track World’s Mood Swings: Work, Sleep and Daylight Play Role

October 18, 2011

Using Twitter to monitor the attitudes of 2.4 million people in 84 countries, Cornell University researchers found that people all over the world awaken in a good mood – but globally that cheer soon deteriorates once the workday progresses.

By tracking Twitter tweets over two-years, researchers determined that work, sleep and the amount of daylight all play a role in shaping cyclical emotions such as enthusiasm, delight, alertness, distress, fear and anger.

Researchers have long known about these affective rhythms, but have relied on small homogeneous samples and have had no practical means for hourly and long-term observation of individual behavior in large and culturally diverse populations. Before the rise of social media, these kinds of results were inconclusive, according to the researchers Scott Golder, Cornell graduate student in sociology; and Michael Macy, Cornell professor of sociology. Their paper, “Diurnal and Seasonal Mood Tracks Work, Sleep and Daylength Across Diverse Cultures,” was published in the journal Science.

Using Twitter in conjunction with language monitoring software, Golder and Macy discovered two daily peaks in which tweets represented a positive attitude – relatively early in the morning and again near midnight, suggesting mood may be shaped by work-related stress. Positive tweets were also more abundant on Saturdays and Sundays, with the morning peaks occurring about two hours later in the day. This implies people awaken later on weekends.

These patterns were reflected in cultures and countries throughout the world, but shifted with the difference in time and work schedule. For example, positive tweets and late-morning mood peaks were more prominent on Fridays and Saturdays in the United Arab Emirates, where the traditional workweek is Sunday through Thursday, according to the paper.

Golder and Macy also tracked global attitude on a seasonal basis to determine if “winter blues” is represented in Twitter messages. While no correlation was discovered between absolute daylight and mood, there was a correlation when examining relative daylight, such as the gradually decreasing daylength between the summer and winter solstices.

From: National Sleep Foundation publication

Childhood Obesity and Bedtime Preference

October 28th, 2011 Raquel Rothe

A study published in the October issue of the journal SLEEP from American Academy of Sleep Medicine:


“Scientists have realized in recent years that children who get less sleep tend to do worse on a variety of health outcomes, including the risk of being overweight and obese,” said study co-author Carol Maher, PhD. “[The study] suggests that the timing of sleep is even more important.”

Sleeping Well While Sitting Up? This WebMD member can’t fall asleep while lying down. Have you had a similar problem?

October 7th, 2011 Raquel Rothe

Great article to share if you are having difficulty sleeping except in strange positions


Words to expand your sleep vocabulary-#13

July 9th, 2011 Raquel Rothe


From the Latin meaning “about a day,” circadian refers to numerous phenomena (especially biological rhythms) that have an interval length of approximately 24 hours. It may be used in reference to circadian rhythm sleep disorders.

Words to expand your sleep vocabulary-#9

June 26th, 2011 Raquel Rothe

Jet lag

Jet lag is a temporary condition that is caused by rapid travel across time zones — as may occur with jet trips — and may leave an individual experiencing fatigue, insomnia, nausea, or other symptoms as a result of the internal circadian rhythm, or biological clock, being misaligned with local time.

Words to expand your sleep vocabulary-#1

May 9th, 2011 Raquel Rothe


From the German for “time giver,” zeitgeber refers to any external cue that can entrain (or reset) the time-keeping system of organisms. In humans, this circadian system, or biological clock, is located in the suprachiasmatic nucleus within the hypothalamus of the brain. This system is affected by zeitgebers. These cues follow a periodic pattern. The strongest zeitgeber is the natural pattern of light and darkness.