Circadian rhythm

The theory part

"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)

Before the artificial lights became common, evenings and nights were much darker for us than they are nowadays. I'm a good example of the curernt situation. Outside, there is almost complete darkness. I couldn't see anything if the street lamps were removed. Inside, I'm seeing light from three different lamps plus TV and computer.

Also, in the past, days were much brighter than today. Because the indoors are covered with ceilings and window blinds, the total brightness can easily be 1000 times less than in outdoors:

"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'?)

Also, there is a third problem too related to our circadian rhythm: we are sleeping too little. According to a recent review article evalution the link between sleep and obesity, people slept 8-9 hours on average in the 60s. At 1995 the average lenght sleep had been reduced to 7 hours. Some recent studies based on actigraphy and polysomnography suggest that nowadays, middle-aged people are sleeping six hours a night on average. (Reiter et al. 2011)

A little proportion of population are doing shift work. The studies about these people can possibly tell us, what kind of problems the interruption of circadian rhythm might cause:

• A Swedish population-based study consisting of 27485 persons reported 40% higher (adjusted) obesity risk in those who were doing shift work. (Karlsson et al. 2001)
• Danish nurses who are doing shift work (day and night shifts) have 80% higher breast cancer risk than those not doing shift work. Those who had done shift work for more than 2 years had even 160% higher risk even after many statistical adjustments.(Hansen&Stevens 2011)
• In Netherlands a little study of 122 people reported higher hair cortisol in people doing shift work (47.32 vs 29.72 pg/mg). Young shift works had significantly higher BMI than young non-shift workers. (27.2 vs 23.7). (Manenschijn et al. 2011) 
• In an Italian study, 220 shiftworkers and 442 dayworkers had some thyroid labs tested. 3.8% of dayworkers had subclinical hypothyroidism, but up to 7.7% of shiftworkers had the same condition.  (Magrini et al. 2006 ; Perfect Health Diet - Intermittent Fasting as a Therapy for Hypothyroidism)

"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...)

There are also some interesting sleep restriction studies:

• The researchers of University of Chicago conducted a study in which they had eleven young men whose sleep was restricted to 4 hours a night, for six days. The sleep deprivation caused their cortisol levels to rise, and their sugar tolerance worsened too. (Spiegel et al. 1999)
• Many years later there was another interesting piece of research conducted in the same university. It was a cross-over study in which people ate a calorie-restricted diet and their slept was restricted to either 5.5 hours a night (actual duration 5h 14min) or 8.5 hours a night (actual duration 7h 25min). The sleep deprivation didn't impair weight loss, but it made people to lose more muscle and less fat (80% fat and 20% muscle vs. 48% fat and 52% muscle). So, sleep well if you wanna lose fat in a healthy way. (Nedeltcheva et al. 2010 ; Whole Health Source - The Big Sleep)

Our circadian systems react to environmental lights. Blue light (especially 460-490nm) blocks melatonin secretion of pineal gland. In darkness or in light that doesn't contain blue wavelenghts, melatonin secretion is increased. This has been studied with so-called blue blocker lenses, which block most of the blue light (Sasseville et al. 2006, Kayumov et al. 2007) and lamps with different hues (Chellappa et al. 2011, Meesters et al. 2011). Blockade of blue light might be a good thing in the evening, because even normal room light might affect nocturnal melatonin secretion. The effect might be significant especially in the wintertime because in the absense of sufficient daylight body reacts more strongly to the evening illumination (Gooley et al. 2011, Higuchi et al. 2007, Park&Tokura 1999). I'm not completely sure how important this melatonin system is to the whole circadiam system, because melatonin isn't the only hormone with circadian rhythm. Cortisol levels are affected by all kinds of light, even red light (Figueiro&Rea 2010, Leproult et al. 2001). Below are some clinical studies in which modification of light has led to interesting results:

• Japanese researchers observed that quite a bright artificial light (5000 luksia) in the daytime might improve the carbohydrate digestion after the evening meal and that similar light in the evening might cause opposite effects (Sone et al. 2003, Hirota et al. 2003). (Also read: Acne.org forum - A Zinc-less Zinc Regimen for Adults: Draft 4)
• Burkhart&Phelps from University of Toledo made a little trial in which they investigated the effect of blue blocker glasses on sleep. Orange blue blocker glasses improved sleep and mood, but yellow-tinted control glasses did not. (Burkhart&Phelps 2009)
• In the Dr. James Phelpsi' article about dark therapy and bipolar disorder, a little experiment is described. Some people (n=21) with bipolar disorder and some sleep problems too, were given blue blocker glasses.for evening usage. The condition of nine participants improved "very much", while eight didn't notice difference. A few people noticed a little benefit or a little disbenefit to their condition. (Phelps 2008).(Also read Seth Roberts' Bipolar Disorder: Good Results With Blue-Blocker Glasses)
• In the state of NY, some schoolchidren were adviced to use blue blocker glasses during their schooldays. Because of this, their melatonin levels started to rise half a hour later than usually (in the evening) (Figueiro&Rea 2010).
• Light therapy seems to be beneficial for some conditions such as depression and seasonal affective disorder (Golden et al. 2005, Lieverse et al. 2011).

I could imagine that the benefits caused with light therapy could be exceeded with natural daylight. Why? You can possibly get 10 000 lux of light to your eyes from a expensive light therapy device. When you go outside, if might be many-fold brighter out there. Especially in the summertime daylight might have other benefits, such as vitamin D production and temporarily lowered blood pressure caused by ultraviolet radioation. (Holick et al. 2007, Opländer et al. 2009, Feelisch et al. 2010).

Another way to affect our circadian clock is eating melatonin supplements.

• Melatonin can be used as a therapy for insomnia and it seems to work quite well in some people (seemingly 0.3mg is a very sufficient dose, despite the higher amounts in many preparations). (Wade et al. 2011, Rondanelli et al. 2011, Zhdanova et al. 2001, Lemoine et al. 2007)
• In one study melatonin relieved participants' IBS (irritable bowel syndrome) symptoms. (Lu et al. 2005)
• Melatonin also seems to be a powerful therapy for GERD/heartburn. (Pereira 2006, Kandil et al. 2010)
• One recent article also suggests that melatonin might even help people with fibromyalgia. The benefit might be related to improved sleep quality because the subjects in melatonin supplementation groups had a significant improvement in their sleep parameters. (Hussain et al. 2011)

Some health bloggers have also been suggesting that in addition to light, eating and possibly even movement might affect circadian system. Because of this, some health bloggers have written of the importance of eating during daylight hours. I know little of this, but there might be real research behind these ideas (Fuller et al. 2008). It has also been reported that even seeing people might affect circadian clock. Seth Roberts, for example, has written how watching faces (from mirror or TV) after awakening might improve mood and bipolar disorder.



My recommendations

1. Spend some time outside every day. If only possible, use your computer on balcony instead of indoors.

• Daylight is usually better than light boxes, but if you can't spend much time outside, some extra daytime light for artificial sources might be healthy.
  

2. When the sun goes down, black out your room. If you use computer before going to sleep, darken your screen as much as possibly (you might need to open your graphics card control panel and so on...). If you don't like the idea, at least download f.lux.


3. Get blue blocker glasses for evening usage. Some blue blocker glasses are very expensive, but the cheap versions you can easily find from Amazon or eBay are probably good enough. Keywords: "blue blocker" or "uvex espresso" (Uvex' Espresso lenses block 85% of light and more than 95% of all blue light.)

Some extra resources:
Perfect Health Diet - Seth Roberts and Circadian Therapy
Perfect Health Diet - Intermittent Fasting as a Therapy for Hypothyroidism
CNN: Trouble sleeping? Maybe it's your iPad
NY TIMES: In Eyes, a Clock Calibrated by Wavelengths of Light
NY TIMES: Sleeping (or Not) by the Wrong Clock
Independent: Could you be suffering from 'social jet lag'?
Slumber's Unexplored Landscape - People in traditional societies sleep in eye-opening ways
Telegraph: This could be your dream diet
Can lamps cause epileptic or other types of seizures?

Some extra papers that might be related to this topic..:
Relationship between individual difference in melatonin suppression by light and habitual bedtime.
Melatonin in walnuts: influence on levels of melatonin and total antioxidant capacity of blood.
Altered sleep architecture and higher incidence of subsyndromal depression in low endogenous melatonin secretors.
Effect of sunlight exposure on cognitive function among depressed and non-depressed participants: a REGARDS cross-sectional study.
Narrowband ultraviolet B phototherapy improves the quality of life in patients with psoriasis.
Working under daylight intensity lamp: an occupational risk for developing circadian rhythm sleep disorder?