Several large population studies, as well as lab
experiments, have shown a clear link between a woman's
exposure to light at night and breast cancer. A similar
link has been shown with prostate cancer in men. The
risk is greatly increased for:
== Those who frequently do not go to sleep until after
== Those who have the brightest bedrooms
== Late-night shift workers (and the longer they work
nights, the greater the risk)
A study published in the Journal of the National Cancer
Institute concludes that this is the result of a chronic
suppression of melatonin - an anti-cancer hormone that
is produced by the body only in the dark.
The solution? Get to bed before midnight (production of
melatonin peaks at 1:30 a.m.), sleep in a completely
dark room, and if you work at night, consider switching
to daytime hours (especially if you have a family
history of cancer).
Note that it's not just the number of hours of sleep that is important to health, but the darkness as well.
You can go to the Journal of the National Cancer Institute
It does? The body has a teeny tiny little clock that tells melatonin when it's 1:30 a.m.?
Yes, it does.
Not necessarily for the actual clock time, but for the darkness time. And this "teeny tiny little clock" goes haywire if we veer away from actual darkness time.
And not only for melatonin (it's also the first time I heard of 1:30 am), but also for other hormones like corticosteroids (before 10 am) and growth hormone and IGF (around 10 pm, IF asleep). (Yes, that's an "am" for corticosteroids.) It's probably true for other body functions as well. In poultry, chick growth is enhanced by controlling the number of hours of brightness and darkness.
So the "1:30 am" time may not really be the actual time melatonin is released, but rather the "so many hours" after sunset, which is definitely affected by our lighting after sunset. Shifting between real time to daylight savings time may even have its effects as well.
I also don't know if it's a function of darkness or deep sleep, but circulation is also similarly subject to diurnal cycles. During the hours after midnight, circulation is shifted to the skin, away from internal organs, which is why chemo is best given in those hours (to "bypass" liver, kidneys or bone marrow). Of course, circulation continues throughout the body, but the blood flow -- amount -- is not the same throughout the day in various organs or regions of the body. In Chinese t'ien hsueh or dim mak, striking certain body points at particular times of the day can increase the killing effect of such strikes, indicating diurnal cycles of ch'i or qi.
I read or heard this years ago, Gerry, and why I stopped
sleeping with a light on in my bedroom. Also why I began
going to bed earlier.
It used to take me forever to get to sleep - I think it was
because I missed my 'sleeppy time', that inner clock thing.
No longer any problems.
Can you point to a credible source for this information? (As you can see, I should be getting to bed earlier.)
I don't have the references around right now.
The corticosteroid thing is a "standard textbook" item because administration of extraneous corticosteroids is recommended to be in the morning before 10 am to best imitate the body's cycle.
I came across the growth hormone/IGF thing from bodybuidling mags. I don't know how credible you would think these are, but I've found pretty deep biochemical/physiological stuff in their pages during the time that my brother bought a lot of them.
As for the melatonin secretion, I think the articles in the Journal of the National Cancer Institute provide the proofs of the cycle, if not the effectivity against cancer (contrary articles about the latter).
From the introduction of this study: Eva S. Schernhammer, Francine Laden, Frank E. Speizer, Walter C. Willett, David J. Hunter, Ichiro Kawachi, and Graham A. Colditz. Rotating Night Shifts and Risk of Breast Cancer in Women Participating in the Nurses' Health Study J Natl Cancer Inst 2001; 93: 1563-1568:
The suprachiasmatic nucleus in the hypothalamus, one of the most important physiologic determinants of alertness and performance, drives a circadian pacemaker in mammals, with an intrinsic period averaging 24 hours. Light is the primary stimulus to disrupt and reset this pacemaker, which is expressed in changing melatonin rhythms. Light exposure at night may, therefore, be related to a variety of behavioral changes and associated health problems not yet well explored. Studies (1) have suggested an increased risk of coronary heart disease among rotating night shift workers, not fully explained by an increased prevalence of coronary risk factors. Others have linked night work to an increased breast cancer risk among women (2).
The studies referred to (1 and 2) are:
1 Kawachi I, Colditz GA, Stampfer MJ, Willett WC, Manson JE, Speizer FE, et al. Prospective study of shift work and risk of coronary heart disease in women. Circulation 1995;92:3178–82.
2 Hansen J. Increased breast cancer risk among women who work predominantly at night. Epidemiology 2001;12:74–7.
Ruby, I have done a book report with my son about Rythem, (it was way above his head) and everything Gary said is right. I do not want to waste my time to go dig out the books we read for this report, but I do remember that the experiments were done in underground rooms where the subjects had no way of knowing the time of day, whether it was day or night, and they were tested on a number of things, including blood pressure, heart rate, hormones etc. and there was a rythem to things according to the time of day, even if the subjects were not aware of the time.
What Gary is saying is well tested and documented, you do your own research on your own time, it is out there.
I thought your body should adjust too, it just makes sense that it should. However certain things were set to go with the rythem of your body no matter what, it said it is like having a little clock inside your body and things run according to that clock.
I am trying to remember how long the subjects stayed in this location, which should make a difference, but it is not coming back to me...