Night Light Pollution Linked to Breast Cancer, Particularly for Asian Populations, ER+ Cases

Molecular mapping on a computer | Image Credit: JR-50 - stock.adobe.com.jpeg

An increased risk of breast cancer was observed in light at night (LAN) exposure, often leading to decreased melatonin levels, specifically significant among Asian populations. With the emergence of artificial night lights, light pollution has intensified as an environmental issue through urbanization and industrialization.

A meta-analysis of 21 eligible studies (8 cohort, 13 case-control) published between 2001 up to 2023 analyzed 734,372 participants exposed to light pollution. The average follow-up time period was 12.8 years among 11 North American studies, 3 European, 5 Asian, and 2 Australian.

Calculations used the adjusted relative ratios (RR) and 95% CIs to assess the association between breast cancer incidence and LAN exposure.

Eligible studies included 42.9% focused on estrogen receptor status, 47.6% accounted for menopausal status, 66.7% investigated indoor and outdoor LAN (n = 9, 10, 14, 14, respectively).

In Asia, the breast cancer incidence rate was higher than in North America (RR, 1.24 vs 1.11; P < .001 for both). No statistically significant differences were found in the breast cancer incidence rate in Europe (RR, 0.99; 95% CI, 0.89-1.11; P = .898).

White populations had higher incidences of breast cancer risk when compared with the observed Black populations (RR, 1.12 vs 1.15; P < .001 vs P = .080).

Outdoor LAN exposure reportedly had a slightly higher effect on breast cancer incidence than indoor LAN exposure (RR, 1.07 vs 1.02; P = .004 vs P = .675).

Stronger impacts on breast cancer risk from LAN exposure for cases with estrogen receptor positivity were compared with cases with estrogen receptor negativity (RR, 1.10 vs 1.07; P = .005 vs P = .316).

Significant associations between exposure to LAN and the risk of breast cancer was demonstrated (RR, 1.12; P < .001).

Overall, the highest breast cancer risk was found in the Asian population and estrogen receptor (ER) statuses (Asian: RR, 1.24; ER-positive 1.10; P < .001 vs P = .005).

The meta-analysis has limitations such as uncontrolled confounding factors that can affect evaluations and small sample sizes, which ultimately limits the available data. There was also no updated outdoor LAN dose date available after 2021. Subjectivity is also present and cannot be avoided within the selection.

There were no statistical significances between breast cancer risk between pre-and postmenopausal women exposed to LAN. Findings indicate the stronger relationships among certain subgroups, like study populations located in Asia or investigations focusing on LAN exposure. Study results contribute to the identification of important future research topics while offering meaningful recommendations.

Reference

Luo Zhi-Quan, Liu Z, Chen H, Liu Y, Tang N, Li H. Light at night exposure and risk of breast cancer: A meta-analysis of observational studies. Front Public Health. 2023;11:1276290. doi:10.3389/fpubh.2023.1276290