Measuring Light at Night and Melatonin Levels in Shift Workers: A Review of the Literature

Jun 20, 2017Biological research for nursing

Light Exposure at Night and Melatonin Levels in Shift Workers: A Literature Review

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Circadian Biology on OpenScience ↗PubMed ↗DOI ↗

Abstract

Shift work is associated with an increased risk of diseases, including cancer.

Six studies focused on the relationship between light at night (LAN), melatonin levels, and cancer risks in shift workers.
Circadian disruption linked to shift work may contribute to higher disease risks, particularly for cancer.
Contradictory findings and inconsistent methods have complicated the establishment of a direct link between LAN and disease.
Improved protocols for measuring personal LAN exposure are needed to better understand its effects on health.
Field measurements of circadian disruption and melatonin levels could help clarify existing discrepancies in research findings.

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Shift work, especially that involving rotating and night shifts, is associated with an increased risk of diseases, including cancer. Attempts to explain the association between shift work and cancer in particular have focused on the processes of melatonin production and suppression. One hypothesis postulates that exposure to light at night (LAN) suppresses melatonin, whose production is known to slow the development of cancerous cells, while another proposes that circadian disruption associated with shift work, and not just LAN, increases health risks. This review focuses on six studies that employed quantitative measurement of LAN and melatonin levels to assess cancer risks in shift workers. These studies were identified via searching the PubMed database for peer-reviewed, English-language articles examining the links between shift work, LAN, and disease using the terms light at night, circadian disruption, health, risk, cancer, shift work, or rotating shift. While the results indicate a growing consensus on the relationship between disease risks (particularly cancer) and circadian disruption associated with shift work, the establishment of a direct link between LAN and disease has been impeded by contradictory studies and a lack of consistent, quantitative methods for measuring LAN in the research to date. Better protocols for assessing personal LAN exposure are required, particularly those employing calibrated devices that measure and sample exposure to workplace light conditions, to accurately assess LAN's effects on the circadian system and disease. Other methodologies, such as measuring circadian disruption and melatonin levels in the field, may also help to resolve discrepancies in the findings.

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Measuring Light at Night and Melatonin Levels in Shift Workers: A Review of the Literature

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Recent issues from the circadian biology brief