27 juli 2005: J Natl Cancer Inst. 2005 Jul 20;97(14):1084-7 en The Globe

Melatonine waarden in de ochtend urine geven risico aan op krijgen van borstkanker lijkt een deelstudie uit een veel grotere studie naar effect van melatonine waarden op risico van kanker te bevestigen. Hoe lager het melatonine gehalte hoe groter het risico op krijgen van borstkanker en het verschil kan oplopen tot wel 40%. Vrouwen die regelmatig en goed slapen 's nachts in het donker - de melatonine wordt dan perfect aangemaakt - hebben hogere melatonine waarden dan vrouwen die bv. door nachtdiensten regelmatig ook overdag slapen of op andere wijze vaker slapen in het licht. Het gevolg is dat de laatste groep vrouwen een soms tot 40% grotere kans op het krijgen van borstkanker hadden. Lees hier het abstract van de studie en daaronder een artikel uit The Globe over deze studie gepubliceerd in National Journal of Cancer, een van de meest toonaangevende tijdschriften over kanker ter wereld.

J Natl Cancer Inst. 2005 Jul 20;97(14):1084-7.

Urinary melatonin levels and breast cancer risk.

Schernhammer ES, Hankinson SE

. Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA. eva.schernhammer@channing.harvard.edu

Exposure to light at night suppresses melatonin production, and night-shift work (a surrogate for such exposure) has been associated with an increased risk of breast cancer. However, the association between circulating melatonin levels and breast cancer risk is unclear. In a prospective case-control study nested within the Nurses' Health Study II cohort, we measured the concentration of the major melatonin metabolite, 6-sulphatoxymelatonin (aMT6s), in the first morning urine of 147 women with invasive breast cancer and 291 matched control subjects. In logistic regression models, the relative risk (reported as the odds ratio ) of invasive breast cancer for women in the highest quartile of urinary aMT6s compared with those in the lowest was 0.59 (95% confidence interval = 0.36 to 0.97). This association was essentially unchanged after adjustment for breast cancer risk factors or plasma sex hormone levels but was slightly weakened when the analysis included 43 case patients with in situ breast cancer and their 85 matched control subjects (OR = 0.70, 95% CI = 0.47 to 1.06). The exclusion of women who had a history of night-shift work left our findings largely unchanged. These prospective data support the hypothesis that higher melatonin levels, as measured in first morning urine, are associated with a lower risk of breast cancer.

PMID: 16030307 [PubMed - in process]

Hier het artikel uit The Globe over deze studie

Breast Cancer Risk Linked To Sleep Patterns

By Andre Picard
The Globe and Mail

One of the most effective ways to reduce the risk of breast cancer may be to regularly get a good night's sleep -- in the dark.

A new study shows that women with the highest levels of melatonin -- a hormone the body produces only when a person is sleeping at night, in the dark -- have a breast cancer risk that is 40 per cent lower than those with low levels of melatonin.

Dr. Eva Schernhammer, an epidemiologist at Brigham and Women's Hospital in Boston, said the research suggests that "melatonin secretion may play an important role in breast cancer development." She said that when and how well a woman sleeps may also influence whether she develops breast cancer, and that sleep patterns could also have an impact on tumour development and, by extension, on the effectiveness of treatment.

The research, published in today's edition of the Journal of the National Cancer Institute, seems to confirm the long-held hypothesis about the cause of sharply higher breast cancer rates among shift workers. A number of studies have shown that workers who regularly toil on the late-night shift, such as nurses, are about twice as likely to develop breast cancer as those who work day shifts. Disruption of melatonin production was long suspected as the culprit, but it was only a theory, based on a retrospective look at the work habits of cancer patients. The new study by Dr. Schernhammer and a team at Harvard University is different in that the researchers actually measured levels of melatonin in the urine of women before and after they developed breast cancer. The research is an offshoot of the massive Harvard Nurses Study, in which the health of almost 120,000 nurses has been tracked since 1989. As part of that project, more than 30,000 women have provided regular urine samples.

The new study by Dr. Schernhammer focused on 147 women who developed breast cancer; they were compared with 291 women of similar background who did not develop it. Melatonin production peaks at night, and exposure to light at night interrupts production of the hormone. When this occurs, it also stimulates a women's ovaries to produce extra estrogen; excess production of the female sex hormone is a known risk for breast cancer. The idea that too much exposure to light can raise a woman's cancer risk derives from earlier research on blind women, who are half as likely to develop breast cancer as sighted women. In blind women, melatonin levels do not fluctuate and, as a result, their estrogen levels are more stable.
In the new study, researchers found that melatonin levels were sharply lower in women who developed breast cancer, even well before their diagnosis. Among the 25 per cent of women with the lowest levels of melatonin, 50 developed breast cancer; by comparison, among the 25 per cent with the highest levels of melatonin, 23 developed breast cancer.

Dr. Schernhammer said the results suggest that the melatonin is influencing risk, not the shift work itself. This year, an estimated 21,600 women and 150 men will be diagnosed with breast cancer, according to the Canadian Cancer Society, and an estimated 5,300 women and 45 men will die of the disease.

© Copyright 2005 Bell Globemedia Publishing Inc. All Rights Reserved.

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