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Exposure To Artificial Light Increases Risk For Breast Cancer

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Women who are frequently exposed to artificial light at night have a higher risk for developing breast cancer, a long-term study found. This was particularly true among pre-menopausal women who have a history of smoking.

Researchers say that women who are subjected to such exposures have higher risks by as much as 14%. Women who live in areas that have high levels of artificial outdoor lighting at night are particularly vulnerable, Tech Times reports.

Similar studies linking artificial light and breast cancer have been conducted before, but this is possibly the most comprehensive one to take a look at the subject. The researchers examined data from close to 110,000 women enrolled in the Nurses’ Health Study II from 1989 to 2013. They likewise studied night time satellite images of the Earth, focusing on the residential addresses of the participants. Factors such as socioeconomic status and health conditions, as well as night shift work, were included in the study.

Among the participants, there were 3,549 breast cancer incidences reported. The association between artificial light and breast cancer was strongest among pre-menopausal women and women who are smokers, or used to smoke. There was also a strong link between women who works night shifts and breast cancer, suggesting that the combination of artificial light at night while they worked contributed to the increase in risk.

Peter James, assistant professor at Harvard Medical School and lead author of the study, said,

The growing research on light at night and breast cancer is based on data suggesting that exposure to light during nighttime hours suppresses nocturnal secretion of melatonin and disrupts circadian patterns and sleep.

Melatonin is a hormone secreted by the brain that is in charge of sleep and wake cycles. Researchers believe that the effect of melatonin on cancer risk may lie in the idea that disturbing the body’s normal circadian rhythm, or body clock, leads to abnormal cell division.

Further studies are needed to understand the full effects of artificial light on cancer, as previous studies have also linked other forms of cancer to it, such as prostate cancer in men.

The study was published in Environmental Health Perspectives.

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