People who are exposed to high amounts of artificial light at night may be at increased risk of developing thyroid cancer, according to research findings published Feb. 8 in the American Cancer Society's Cancer journal.
Light at night can disrupt both melatonin levels and circadian rhythms, or the body's internal clock. Prior studies have indicated a link between high levels of light at night and elevated breast cancer risk. Given thyroid cancer may share hormone-based characteristics with breast cancer and that circadian rhythms also contribute to regulating thyroid function, the study authors predicted that greater exposure to artificial light during the night would be associated with thyroid cancer.
The study followed 464,371 participants for an average of nearly 13 years. Among those, a total of 856 were diagnosed with thyroid cancer. The highest quintile of light at night exposure was associated with a 55 percent increased risk of developing thyroid cancer, compared to the lowest quintile, according to the study's findings. Additionally, results showed the link was primarily driven by papillary thyroid cancer and was strongest among women.
"We hope our study will motivate researchers to further examine the relationship between light at night and cancer, and other diseases," said Qian Xiao, PhD, lead study author. "Recently there have been efforts in some cities to reduce light pollution, and we believe future studies should evaluate if and to what degree such efforts impact human health."
To view the full study, click here.