Artificial night light and thyroid cancer

ARTICLE HIGHLIGHTS

Research background

The increasing incidence of thyroid cancer (TC) globally has sparked interest in identifying potential environmental factors contributing to this rise. While prior research has explored various risk factors, the association between artificial light at night (ALN) and TC remains an underexplored area. Present status: Current data indicate a notable increase in TC cases, along with a rise in exposure to ALN. Significance of the Study: Our findings imply that intense ALN is indeed associated to financial measures such as gross domestic product (GDP), but it is the latter, and not ALN, which may create conditions that are detrimental to health and a potential risk factor for TC.

Research motivation

The study is motivated by the need to comprehensively investigate the impact of ALN on TC at a global scale, recognizing the ubiquitous nature of light pollution in the modern world. Main topics and key problems: The primary focus is on evaluating the relationship between ALN exposure and TC incidence worldwide. The study delves into the prevalence of ALN using satellite data and examines whether there is a significant association with rates of TC. The research investigates the role of socioeconomic conditions, as indicated by GDP and health expenditure per person (HEP), in contributing to TC incidence. The study incorporates the quality of cancer registries (QCR) as a variable, recognizing the potential impact of data accuracy on the observed relationships. Significance for future research: By exploring the interplay between ALN exposure, socioeconomic factors, and TC, this study lays the groundwork for a more holistic understanding of the risk factors associated with TC. The study contributes to the broader field of environmental determinants of cancer, emphasizing the need for researchers to consider light pollution as a potential lifestyle-related factor impacting cancer risk. Acknowledging the limitations in exploring specific lifestyle factors in this study, future research can delve deeper into understanding the precise elements of lifestyle, such as sleep hygiene and circadian rhythm disruptions, which may contribute to TC risk.

Research objectives

Main objectives: To quantify and assess the prevalence of ALN exposure globally vis-à-vis TC epidemiology, using satellite data and cancer registries, respectively and controlling for financial conditions by country. Realized: Achieved through the analysis of ALN levels exceeding specific thresholds vis-à-vis TC epidemiology. Correlations among different financial indicators with both ALN exposure and TC incidence were noted, providing insights into potential socioeconomic influences. We integrated the QCR as a variable to account for potential variations in data accuracy. Future research: Significance: The study sets the stage for future research by highlighting the intricate relationship between ALN, socioeconomic factors, lifestyle, and TC risk. Future investigations can build upon these insights, delving deeper into specific lifestyle factors and refining preventive interventions.

Research methods

Research Methods Used-Novelty: The study leveraged ALN data to explore its potential association with TC, integrating ALN exposure data with socioeconomic indicators such as GDP and HEP. Moreover, it considered the QCR as a variable that potentially leads to variations in data accuracy. Statistical Analyses: The data were analyzed with the Kolmogorov-Smirnoff, Kruskall Wallis and Kendall's Tau tests.

Research results

The global prevalence of ALN exposure was assessed, revealing that 67.3% of the world's population experiences ALN levels surpassing 87 μcd/m², and 34.6% surpassing 688 μcd/m². Globally, TC incidence, measured by the Adjusted Standardized Rate (ASR), was found to be 4.2 per 100000 population. Significant variations in ASR and ALN exposure percentages were noted across GDP and HEP quartiles, with higher values correlating to higher economic indicators. Differences in ASR were observed concerning the QCR, showing higher ASR in high-quality registries compared to lower quality ones. ASR by GDP and HEP quartiles demonstrated higher rates with increased economic indicators, and ALN exposure percentages also rose with higher economic quartiles. Direct associations between ASR and ALN exposure percentages were not significant. The study underscores the intricate relationship between ALN, economic indicators, and TC, emphasizing the role of socioeconomic conditions in cancer epidemiology. Problems that Remain to be Solved: The study found no direct link between ALN and TC, emphasizing the need for further research to understand their complex relationship. Consideration of QCR is crucial, urging refined assessments of data accuracy.

Research conclusions

New theories proposed: While this study primarily focused on empirical investigations rather than proposing new theoretical frameworks, it introduced a nuanced perspective on the relationship between ALN, socioeconomic factors, and TC. The absence of a direct correlation between ALN and TC challenges existing theories that oversimplify the link between light pollution and cancer risk. The findings encourage a more complex understanding of environmental and socioeconomic influences on cancer incidence, prompting future theoretical developments in this field. New Methods Proposed: The study did not explicitly propose new research methods but demonstrated an innovative approach through the integration of diverse methodologies. Notably, the interdisciplinary analysis, global scale examination and incorporation of socioeconomic indicators represent methodological advancements. The study's emphasis on the QCR as a variable and its statistical analyses contribute to methodological robustness.

Research perspectives

Future research should delve deeper into understanding the complex dynamics between ALN exposure and cancer risk. Investigating specific patterns of light exposure, considering variations in intensity, duration, and timing, may provide a more nuanced understanding of how ALN influences cancer incidence. Future research could also investigate the role of economic factors in shaping lifestyle choices, healthcare access, and environmental exposures, refining our understanding of the socioeconomic mechanisms influencing cancer incidence. Research focusing on the improvement of cancer registry quality assessment methods is crucial. Developing strategies to enhance data accuracy, especially in regions with lower-quality registries, will contribute to more reliable and comparable cancer incidence data. This could involve collaborations to standardize data collection practices globally.