Sleeping Patterns Are Governed by Light

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Sleeping Patterns Are Governed by Light

Posted by: Dr. Mercola
May 20 2008 | 131,331 views

Your biological clock is not the only thing that reminds you to shut eye every 24 hours; a new study has found that it‘s actually light that governs your sleeping patterns.

Your eyes use light to reset your biological clock through a mechanism that is separate from your ability to see, researchers at Johns Hopkins University found.

Researchers genetically modified laboratory mice so that a particular set of retinal ganglion cells -- the ones that receive input from the rods and cones of the eyes and send information to your brain -- no longer functioned. The mice were still able to use light to see normally, but had great difficulty synchronizing their circadian rhythms to light or dark cycles.

The findings suggest that people who have trouble sleeping or seasonal depression may be having a malfunction that is contributing to their inability to detect light, which in turn may adversely affect their biological clocks.

Sources:

Nature April 23, 2008

The Time of India April 29, 2008

Dr. Mercola's Comments:

This is a CRUCIAL part of health maintenance that many overlook. They are insensitive to the fact that electrical lighting is a relatively recent innovation and less than a century ago this simply was not available. This modern convenience has sabotaged the health of a large percentage of the population for not paying close attention to how to make adjustments for this modern-day convenience.

Organisms evolved to adjust themselves to predictable patterns of light and darkness, in a physiological cycle known as the circadian rhythm. Once artificial light effectively varied the length of a day, the average night's sleep decreased from around nine consistent hours to roughly seven, varying from one night to the next.

The irregularity prevents circadian rhythms from adjusting to a pattern, and creates a state of permanent "jet lag."

So while electricity and efficient lighting have clearly provided major benefits to society, these benefits come with a price -- the betrayal of your inner clock.

If you are interested in finding more information on this vital subject, I highly suggest reading Lights Out: Sleep, Sugar, and Survival by T. S. Wiley and Bent Formby. The authors believe that it is light, not what we eat or whether we exercise, that causes obesity -- and diabetes, heart disease and cancer.

Get the Light Out of Your Bedroom

It would serve you well to do a thorough “light check” of your bedroom, as any source of light -- even one as tiny as the green glow from your clock radio -- could be interfering with your ability to sleep, and more importantly, your long term health and risk of developing cancer.

While it’s typically thought that your biological clock is what tells you when it’s time to wake up or go to sleep, light and dark signals actually control your biological clock. To get more specific, a part of your brain called the Suprachiasmatic Nucleus (SCN) -- a group of cells in your hypothalamus -- controls your biological clock. And the cells that make up your SCN respond to light and dark signals.

Light actually travels through your eye’s optic nerve to your SCN, where it signals your body’s clock that it’s time to wake up. Light also signals your SCN to initiate other processes associated with being awake, such as raising your body temperature and producing hormones like cortisol.

Meanwhile, when your eyes signal to your SCN that it’s dark outside, your body will begin to produce melatonin, a hormone that helps you sleep and radically decreases your risk of cancer. There are many studies on this powerful association. The more your sleep is disrupted by light pollution, the lower your melatonin levels and the greater your risk of developing cancer becomes.

Melatonin is secreted primarily in your brain and at night it triggers a host of biochemical activities, including a nocturnal reduction in your body's estrogen levels. It’s thought that chronically decreasing your melatonin production at night -- as occurs when you’re exposed to nighttime light -- increases your risk of developing cancer.

In fact, one of the first studies linking cancer to light showed that blind women have a 36 percent lower risk of breast cancer compared to sighted women. Why? Because they are unreceptive to light. This means that their bodies maintain high melatonin levels at night regardless of how much light is in the room.

It really is a fascinating system.

What Happens When Your Biological Clock is Disrupted?

Your body depends on your biological clock to steadily regulate your sleep/wake cycle, but when this process gets thrown off balance, it can wreak havoc on your health.

And it is actually quite easy to disrupt your body clock. For instance, all of the following can confuse your body and make it think you should be awake when you should be sleeping, or vice versa:

Staying up late
Working the night shift
Turning on a light in the middle of the night
Using a night light
Switching time zones (jet lag)
Eating in the middle of the night or too close to bedtime

Your body’s internal clocks (you actually have many, in your brain, lungs, liver, heart and even your skeletal muscles) influence so many things -- from your heart rate to body temperature and hormone production -- that when they’re thrown out of whack all kinds of things can happen. For instance, a disrupted body clock may cause you to you gain weight or increase your risk of cancer.

Using Darkness to Help You Sleep

Making simple changes in your bedroom to keep the light out during the night can have a major impact on your sleep quality. Even the chiropractor at my office, Dr. Lloyd Fielder, was surprised at the benefit when he installed blackout drapes in his bedroom.

He was shocked at how much better he felt -- it radically improved the quality of his sleep. Personally, I sleep in a room that is so dark, it’s even pitch black at noon. You can achieve this in your own bedroom by:

Installing blackout drapes
Closing your bedroom door if light comes through it, and even putting a towel along the base to prevent light from seeping in
Getting rid of your electric clock radio (or at least covering it up at night)
Avoiding night lights of any kind
Keeping all light off at night (even if you get up to go to the bathroom) -- this includes the TV!