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Came across the story below (http://blogs.mcall.com/health/2010/10/could-a-nightlight-make-you-f...) which touches on the strong connection between light/ dark and sleep. This relates to the circadian rhythm and the body's release of melatonin and serotonin in the appropriate amounts, at the appropriate times. It's a topic that we haven't talked about enough here on SleepGuide, and it's very rarely, if ever, discussed in the mass media:

Researchers have long shown that obesity leads to lost sleep—usually due to sleep apnea. They’ve also found that lack of sleep leads to weight gain by making you hungrier, slowing your metabolism and triggering depression (which can lead to increased eating).

None of that is surprising to me.

But when I saw this most recent study about sleep and obesity, I did a double take.

In it researchers exposed mice to dim light at night for 8 weeks. These mice gained 50 percent more weight than other mice who had normal periods of light and darkness. Interestingly, the mice who slept with the dim lighting managed to gain more weight even thought they were not physically eating more food than the control group.

They were, however, eating food at different times. “Something about light at night was making the mice in our study want to eat at the wrong times to properly metabolize their food,” said Randy Nelson, co-author of the study and professor of neuroscience and psychology at Ohio State.

If the results carry over to humans, it could mean that the time of day (or night) you consume your meals can make a much bigger difference to the size of your waistline than previously thought.

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I wonder if this is why people who work nights gain weight..without eating more...as they are exposed to light during their normal circadian sleeping time.
it seems very likely, Sherry. In fact, because of the disruption of circadian rhythms/ normal cycles of light and dark, shift workers tend not only to get fatter, but also are hypothesized to have higher rates of cancer.... check out the article excerpted below I found at http://www.litebook.com/news/displaynews.asp?id=60:

Night workers more prone to cancer: WHO
November 29, 2007

by MARIA CHENG (LONDON) Like UV rays and diesel exhaust fumes, working the graveyard shift will soon be listed as a probable cause of cancer.

It is a surprising step validating a concept once considered wacky. And it is based on research that finds higher rates of breast and prostate cancer among women and men whose work day starts after dark.

Next month, the International Agency for Research on Cancer, the cancer arm of the World Health Organization, will add overnight shift work as a probable carcinogen. The American Cancer Society says it will likely follow. Up to now, the U.S. organization has considered the work-cancer link to be “uncertain, controversial or unproven.”

The higher cancer rates don't prove working overnight can cause cancer. There may be other factors common among graveyard shift workers that raise their risk for cancer.

However, scientists suspect that overnight work is dangerous because it disrupts the circadian rhythm, the body's biological clock. The hormone melatonin, which can suppress tumour development, is normally produced at night.

If the graveyard shift theory eventually proves correct, millions of people worldwide could be affected. Experts estimate that nearly 20 per cent of the working population in developed countries work night shifts.

Among the first to spot the night shift-cancer connection was Richard Stevens, a cancer epidemiologist and professor at the University of Connecticut Health Center. In 1987, Dr. Stevens published a paper suggesting a link between light at night and breast cancer.

Back then, he was trying to figure out why breast cancer incidence suddenly shot up starting in the 1930s in industrialized societies, where nighttime work was considered a hallmark of progress. Most scientists were bewildered by his proposal.

But in recent years, several studies have found that women working at night over many years were indeed more prone to breast cancer. Also, animals that have their light-dark schedules switched develop more cancerous tumours and die earlier.

Some research also suggests that men working at night may have a higher rate of prostate cancer.

Because these studies mostly focused on nurses and airline crews, bigger studies in different populations are needed to confirm or disprove the findings.

There are still plenty of skeptics. And to put the risk in perspective, the “probable carcinogen” tag means that the link between overnight work and cancer is merely plausible.

Among the long list of agents that are listed as “known” carcinogens are alcoholic beverages and birth control pills. Such lists say nothing about exposure amount or length of time or how likely they are to cause cancer. The American Cancer Society Web site notes that carcinogens do not cause cancer at all times.

Still, many doubters of the night shift link may be won over by the IARC's analysis to be published in the December issue of the journal Lancet Oncology.

“The indications are positive,” said Vincent Cogliano, who heads up the agency's carcinogen classifications unit. “There was enough of a pattern in people who do shift work to recognize that there's an increase in cancer, but we can't rule out the possibility of other factors.”

Scientists believe having lower melatonin levels can raise the risk of developing cancer. Light shuts down melatonin production, so people working in artificial light at night may have lower melatonin levels.

Melatonin can be taken as a supplement, but experts don't recommend it long-term, since that could ruin the body's ability to produce it naturally.

Sleep deprivation may be another factor in cancer risk. People who work at night are not usually able to completely reverse their day and night cycles.

“Night shift people tend to be day shift people who are trying to stay awake at night,” said Mark Rea, director of the Light Research Center at Rensselaer Polytechnic Institute in New York, who is not connected with the IARC analysis.

Not getting enough sleep makes your immune system vulnerable to attack, and less able to fight off potentially cancerous cells.

Confusing your body's natural rhythm can also lead to a breakdown of other essential tasks. “Timing is very important,” Dr. Rea said. Certain processes like cell division and DNA repair happen at regular times.

Even worse than working an overnight shift is flipping between daytime and overnight work.

“The problem is re-setting your body's clock,” said Aaron Blair, of the United States' National Cancer Institute, who chaired IARC's recent meeting on shift work. “If you worked at night and stayed on it, that would be less disruptive than constantly changing shifts.”

Anyone whose light and dark schedule is often disrupted — including frequent long-haul travellers or insomniacs — could theoretically face the same increased cancer risk, Dr. Stevens said.

He advises workers to sleep in a darkened room once they get off work. “The balance between light and dark is very important for your body. Just get a dark night's sleep.”

Meanwhile, scientists are trying to come up with ways to reduce night workers' cancer risk. And some companies are experimenting with different lighting, seeking a type that doesn't affect melatonin production.

So far, the colour that seems to have the least effect on melatonin is one that few people would enjoy working under: red.




sherry said:
I wonder if this is why people who work nights gain weight..without eating more...as they are exposed to light during their normal circadian sleeping time.
great article Mike!
we here at SleepGuide need to do more to make people aware of how critical a role light and darkness plays in our overall health -- it all revolves around the circadian rhythm and sleep.

Rock Hinkle said:
great article Mike!
I have also found less exposure to the light in the fridge especially before bed reduces GERD .Some times all I have to do is look at food and gain weight. Those night time cravings are strong. Much to learn......Good Sleep all,Chris Neet article Mike
I recall hearing about a study that showed blind people are much less likely to get cancer than are those of us with sight. It had something to do with being in darkness all day and thus having an uninterrupted, regular melatonin production. I'll try to dig up the study.
I would like to see sleepguide get back to the issues of sleep in general. The site has taken on more of a political or economic agenda these days.

Mike said:
we here at SleepGuide need to do more to make people aware of how critical a role light and darkness plays in our overall health -- it all revolves around the circadian rhythm and sleep.

Rock Hinkle said:
great article Mike!
http://www.sleepreviewmag.com/sleep_report/2010-10-20_07.asp

Research News
Researchers Investigating Impact of Lighting Systems on Sleep
Scientists at the Health Protection Agency’s Centre for Radiation, Chemical and Environmental Hazards in the UK are investigating how the changing spectrum of light exposure during the day affects health.

Poorly designed artificial light systems together with spending too little time outdoors can reduce levels of the body clock hormone melatonin, causing sleep disruption.

Dr John O'Hagan, leader of the HPA's Laser and Optical Radiation Dosimetry Group, said, "The spectrum of sunlight changes during the day so the amount of blue light declines as we approach nighttime. People have evolved to react to this cycle so that the level of melatonin builds up as we approach nighttime causing us to feel sleepy. If we get a very different pattern of light over the day and into the evenings, our health can be affected."

The project is initially researching the level of blue light at care homes for the elderly as well as in houses and hospitals. It also aims to investigate the potential link between exposure to artificial blue light at night and sleep disruption.

"We believe the elderly could benefit most from the findings as a large proportion report difficulties with sleeping,” O'Hagan said. “They often have restricted access to time outdoors and their eye lenses gradually yellow over time, which reduces exposure to blue light."

He added, "We know that proper sleep patterns are important to people's health and mental well-being, so it may be possible to improve people's health by making relatively simple improvements to lighting systems in care homes."

The research in hospitals aims to reveal how the sleep patterns of shift workers are affected by artificial lighting. The group will also investigate how patient recovery could be affected.

"We hope this information together with the work in care homes and domestic properties will provide a compelling argument for further investigations, which will compare the health of people with differing exposures to blue light," O'Hagan said.
i like how this article stressed blue light and its connection to the sleep-wake cycle. this is a critical point that we are going to be hearing a lot more about in the coming years.

Rock Hinkle said:
http://www.sleepreviewmag.com/sleep_report/2010-10-20_07.asp

Research News
Researchers Investigating Impact of Lighting Systems on Sleep
Scientists at the Health Protection Agency’s Centre for Radiation, Chemical and Environmental Hazards in the UK are investigating how the changing spectrum of light exposure during the day affects health.

Poorly designed artificial light systems together with spending too little time outdoors can reduce levels of the body clock hormone melatonin, causing sleep disruption.

Dr John O'Hagan, leader of the HPA's Laser and Optical Radiation Dosimetry Group, said, "The spectrum of sunlight changes during the day so the amount of blue light declines as we approach nighttime. People have evolved to react to this cycle so that the level of melatonin builds up as we approach nighttime causing us to feel sleepy. If we get a very different pattern of light over the day and into the evenings, our health can be affected."

The project is initially researching the level of blue light at care homes for the elderly as well as in houses and hospitals. It also aims to investigate the potential link between exposure to artificial blue light at night and sleep disruption.

"We believe the elderly could benefit most from the findings as a large proportion report difficulties with sleeping,” O'Hagan said. “They often have restricted access to time outdoors and their eye lenses gradually yellow over time, which reduces exposure to blue light."

He added, "We know that proper sleep patterns are important to people's health and mental well-being, so it may be possible to improve people's health by making relatively simple improvements to lighting systems in care homes."

The research in hospitals aims to reveal how the sleep patterns of shift workers are affected by artificial lighting. The group will also investigate how patient recovery could be affected.

"We hope this information together with the work in care homes and domestic properties will provide a compelling argument for further investigations, which will compare the health of people with differing exposures to blue light," O'Hagan said.
The only light that can make you fat comes from opening the 'fridge door too often.

We are not animals; studies measuring animal behaviour and then saying that's what we do are nonsense. All our behaviour is mediated by intellect and emotion; two processes animals don't have.

Cancer is a cellular process. Cells fight cancer or they don't. What they don't do is get tired. Our immune system doesn't get fatigued. Indeed, some research says the opposite; that the more it is challenged the stronger it becomes. Some studies seem to indicate that it is our very hygienic environment which is indirectly causing asthma and other auto-immune complaints because youngsters' immune systems aren't being stretched. The old let them eat dirt argument.

Light received via the eyes stimulates the optical system; nothing else. Light received by the skin produces chemicals within the body some of which we know about - vitamin D for example - and probably others we don't.

Lack of sleep may cause depression. What is certain is that depression can cause lack of sleep. Similarly certain is that depression leads to low mood which leads to reduced activity levels (can't be bothered, too tired, what's the point, sort of things). And we all know what reduced activity levels mean....

There is no certainty as to whether sleep is a physical requirement or an emotional one. Fatigue may be exactly what people say it is when they say "I feel tired". Long duration sleep deprivation is put right by a single night's sleep. If there was a physical component to sleep loss then the bounce back would take longer?

Anyway, back to the diet...
I know that light plays a huge role in our body's systems. The Ascending Reticular Activating System (ARAS) is directly effected by light.

http://www.ncbi.nlm.nih.gov/pubmed/19273236

Abstract
Consciousness develops from birth during the early months as the senses and other nervous system functions mature sufficiently to receive, process and store information. Among these is the ascending reticular activating (arousal) system in the brain stem that is responsible for wakefulness and was proposed by Penfield and Jasper more than 50 years ago as the "controlling mechanism for states of consciousness". This concept has remained the most advanced physiological interpretation of consciousness although recent developments offer greater insights into its nature. The ascending arousal system is the source of activation of the thalamocortical and cortical mechanisms for sensory input and facilitates the rapid matching of sensory input and the binding of memory during cognitive processing. Nonetheless, it is proposed that memory is the critical element through which our connection with the world exists without which, despite a fully functional arousal system, consciousness as we know it could not exist. Evidence is presented in support of this concept in addition to the physiological difficulties that must be resolved if consciousness is to be understood.



Brian Smith said:
The only light that can make you fat comes from opening the 'fridge door too often.

We are not animals; studies measuring animal behaviour and then saying that's what we do are nonsense. All our behaviour is mediated by intellect and emotion; two processes animals don't have.

Cancer is a cellular process. Cells fight cancer or they don't. What they don't do is get tired. Our immune system doesn't get fatigued. Indeed, some research says the opposite; that the more it is challenged the stronger it becomes. Some studies seem to indicate that it is our very hygienic environment which is indirectly causing asthma and other auto-immune complaints because youngsters' immune systems aren't being stretched. The old let them eat dirt argument.

Light received via the eyes stimulates the optical system; nothing else. Light received by the skin produces chemicals within the body some of which we know about - vitamin D for example - and probably others we don't.

Lack of sleep may cause depression. What is certain is that depression can cause lack of sleep. Similarly certain is that depression leads to low mood which leads to reduced activity levels (can't be bothered, too tired, what's the point, sort of things). And we all know what reduced activity levels mean....

There is no certainty as to whether sleep is a physical requirement or an emotional one. Fatigue may be exactly what people say it is when they say "I feel tired". Long duration sleep deprivation is put right by a single night's sleep. If there was a physical component to sleep loss then the bounce back would take longer?

Anyway, back to the diet...
http://www.ncbi.nlm.nih.gov/pubmed/1567518

The effect of color temperature of lighting sources on mental activity level.
Deguchi T, Sato M.

Creative Design Center, Dai-Nippon Printing Co. Ltd.

Abstract
The present study was designed to investigate the effects of color temperature of lighting sources on a contingent negative variation (CNV). Eleven male students (mean age, 23.2) volunteered as subjects. The CNV was recorded under three different color temperature conditions (3000 degrees K, 5000 degrees K and 7500 degrees K). The illuminance level was kept at 1000lx. The lighting condition caused no effect on the reaction time of the performance included in the CNV paradigm. On the other hand, the CNV was suggested to be influenced by the lighting condition. Especially, the CNV between 1025 msec to 1125 msec after the warning stimulus (S1) under 7500 degrees K was obviously larger than that under 3000 degrees K. This tendency was observed within the range between 800 msec and 1300 msec. Judging from no correlation between the light condition and reaction time, the concept of readiness potentials has little possibility for explaining the difference in CNV between the lighting conditions. Therefore, the difference in CNV between 3000 degrees K and 7500 degrees K was concluded to be originated from some differences in orienting response. The color temperature of 7500 degrees K was considered to be more activating than the color temperature of 3000 degrees K from the viewpoint of reticular activating system in CNV mechanism.

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