Nighttime Artificial Light Linked to Increased Thyroid Cancer Risk

Dawn O'Shea

February 10, 2021

People living in regions with high levels of outdoor artificial light at night may face a higher risk of developing thyroid cancer, according to the finding of a study published in the journal Cancer.

Among 464,371 American adults aged 50 to 71 years in 1995-1996 who were followed for an average of 12.8 years, 856 cases of thyroid cancer were diagnosed (384 in men and 472 in women). When compared with the lowest quintile of light at night, the highest quintile was associated with a 55 per cent higher risk of developing thyroid cancer. The association was primarily driven by papillary thyroid cancer, and it was stronger in women than in men.

In women, the association was stronger for localised cancer with no sign of spread to other parts of the body, while in men, the association was stronger for more advanced stages of cancer. The association appeared to be similar for different tumour sizes and across participants with different sociodemographic characteristics and body mass index.

The authors said the association may be related to the fact that light at night suppresses melatonin, which is a modulator of oestrogen activity that may have important anti-tumour effects.    

Zhang D, Jones RR, James P, Kitahara CM, Xiao Q. Associations between artificial light at night and risk for thyroid cancer: a large U.S. cohort study. Cancer. Published online February 8, 2021. DOI: 10.1002/cncr.33392. Abstract

This article originally appeared on Univadis, part of the Medscape Professional Network.

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