Abstract

Overview of the Study

Increasing exposure to artificial light at night (LAN) may disrupt circadian rhythms and influence cancer risks, including thyroid cancer. This research explores the potential link between nighttime light exposure and the incidence of thyroid cancer within a significant U.S. cohort.

Study Background

• LAN exposure could inhibit the secretion of melatonin, disrupting natural circadian rhythms, a suspected risk factor for various cancers.
• Previous research indicates a connection between high LAN exposure and a rise in breast cancer, prompting further investigation into its association with thyroid cancer—a cancer type potentially sharing hormonal etiologies and reliant on circadian rhythm regulation.

Research Methods

The study utilized data from the National Institutes of Health-American Association of Retired Persons Diet and Health Study, estimating LAN exposure through satellite data correlated with participants' residential addresses. The ascertainment of thyroid cancer incidence was conducted via linkage to state cancer registries and analyzed with a Cox regression approach, taking into account demographic, lifestyle, and other environmental factors.

Key Findings

• A positive association was found between high levels of LAN exposure and an elevated risk of thyroid cancer, particularly the papillary type.
• The risk increase was significant, especially in women, with a hazard ratio of 1.81 as opposed to 1.29 in men.
• This association varied by cancer stage and localized versus advanced stages in different genders.

Conclusions

The findings suggest that LAN is indeed positively associated with thyroid cancer risk, necessitating further studies to confirm these results and uncover the underlying biological mechanisms.