Researchers find link between street lighting and breast cancer

New research suggests that there may be a link between street lighting and breast cancer.

Women living in brightly-lit neighbourhoods were found to be at a higher risk of developing breast cancer, according to the long-term study from Harvard University. Researchers analysed data from over 100,000 women in the US between 1989 and 2013, taking note of where these women lived to determine how brightly lit the areas were at night. They also took into account other cancer risk factors including weight and age. The results showed a strong correlation between exposure to higher levels of electric light at night (LAT) and developing breast cancer later in life - those with the highest level of LAT exposure had an 14% increased risk of breast cancer during the study period. However, the risk found in this study was only greater in premenopausal women who were current or ex-smokers. It was also greater among night shift workers. Previous research had found a link like this, reports Romper, but light rays are not associated with cancer. The answer may lie in the fact that artificial light can affect the production of melatonin, a sleep hormone. The researchers surmised that a lack of melatonin and a disrupted sleeping pattern could lead to cancer.

"In our modern industrialized society, artificial lighting is nearly ubiquitous," said the study's lead author Peter James, assistant professor at Harvard Medical School’s Department of Population Medicine. "Our results suggest that this widespread exposure to outdoor lights during nighttime hours could represent a novel risk factor for breast cancer."

It's not clear whether artificial light could be a factor in the development of breast cancer in men. Other research has previously shown that street lighting could also affect breast cancer drugs. Dim light exposure was found to make some cancers resistant to the drug tamoxifen, but supplements of melatonin helped to combat this, according to The Telegraph.