Associations between artificial light at night and risk for thyroid cancer: A large US cohort study

Abstract

Overview

Recent research has discovered a potential link between artificial light at night (LAN) and an increased risk of thyroid cancer. This study investigates the connection within a large cohort from the United States, focusing on how exposure to LAN might contribute to the incidence of this disease.

Background

• Light at night is known to disrupt the secretion of melatonin and may disturb circadian rhythms.
• Previous studies have noted an association between high LAN exposure and elevated breast cancer risk, which shares similar hormonal pathways with thyroid cancer.

Methods

The study utilized data from the NIH-AARP Diet and Health Study, incorporating LAN exposure estimates from satellite images linked to participants' residential addresses. The incidence of thyroid cancer was tracked through state cancer registries, and the data analyzed using Cox regression methods adjusted for various demographic and lifestyle factors.

Findings

Analysis of data from 464,371 participants indicated a significant association between high LAN exposure and increased thyroid cancer risk:

• Individuals in the highest quintile of LAN exposure had a 55% increase in thyroid cancer risk compared to those in the lowest quintile.
• The risk appeared to be more pronounced in women, particularly for localized cancer, while in men the association was stronger for more advanced cancer stages.
• The results were consistent across different tumor sizes and were primarily related to papillary thyroid cancer.

Conclusion

The study's results support the hypothesis that exposure to higher levels of artificial light at night is associated with a heightened risk of developing thyroid cancer. It underscores the need for further studies to confirm these findings and explore the biological mechanisms involved.