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Does the night exposure of light harm people with breast cancer?
Can nighttime exposure to low light have a negative impact on the spread of breast cancer? Researchers have now found that nighttime exposure to low light causes a circadian disorder that increases the formation of metastatic breast cancer in the bone.
A recent study by Tulane University Orleans showed that even light night light increases the formation of metastatic breast cancer in the bone. The results of the study were presented at ENDO 2019, the annual meeting of the Endocrine Society.
Are we exposed to too much light at night?
"To date, it was still unclear that nighttime exposure to low light causes a circadian disorder that increases the formation of metastatic breast cancer in the bone," explains study author Dr. Muralidharan Anbalagan of Tulane University in a press release from the Endocrine Society. This finding is very important, since many breast cancer patients are exposed to excessive light in the bedroom (from mobile devices and other sources) or at work during the night shift, for example.
Breast cancer can affect the bones and cause great pain
According to an estimate by the National Cancer Institute, in 2017 alone, more than 150,000 U.S. women suffered from breast cancer that metastasized or spread outside the breast. When breast cancer spreads, it often reaches the bones, where it can cause severe pain and brittle bones.
Melatonin protects against cancer and promotes sleep
In their study, the researchers created a mouse model for bone metastases. They injected so-called estrogen receptor-positive human breast cancer cells, which have a low tendency to grow in the bones of the tibia of female mice. The animals were then exposed to a strong nocturnal circadian melatonin signal. It was shown that this nocturnal melatonin signal causes strong anti-cancer effects and also promotes sleep.
How was the experiment set up?
All mice were exposed to light for twelve hours every day. A group of mice spent the remaining twelve hours in the dark, which helped them produce high levels of endogenous melatonin. Another group of animals spent twelve hours in the light, followed by twelve hours in low light at night, which suppresses their nighttime melatonin production. The dim light was 0.2 lux, which is weaker in strength than a typical night light or the display of a cell phone. X-rays then showed that mice exposed to a light-twilight cycle had much larger tumors and increased bone damage compared to mice kept in a normal light-dark cycle. The current research has identified the importance of an intact nocturnal circadian melatonin-cancer signal for the suppression of the growth of a bone metastatic breast tumor, the researchers emphasize. The aim of the study was to find an effective way to inhibit or suppress the progression of breast cancer metastases in the bones. (as)