Factors associated with variability in the melatonin suppression response to light: A narrative review

ABSTRACT

Light is the main environmental signal synchronizing circadian rhythms to the 24-hour light-dark cycle. Recent research has identified significant inter-individual variability in the sensitivity of the circadian system to light as measured by, among other indicators, melatonin suppression in response to light. These inter-individual differences in light sensitivity could result in differential vulnerability to circadian disruption and related impacts on health. A growing body of experimental evidence points to specific factors which are associated with variability in the melatonin suppression response; however, no review to date has summarized this research to present a comprehensive summary of current knowledge. The aim of this review is to provide an overview of the state of this evidence, which to date spans demographic, environmental, health-related, and genetic characteristics. Overall, we find that there is evidence of inter-individual differences for the majority of the characteristics examined, although research on many factors remains limited. Knowledge of individual factors that are linked to light sensitivity could inform improved lighting personalization, as well as the use of measures of light sensitivity to determine disease phenotypes and treatment recommendations.

KEYWORDS:

• Circadian
• light sensitivity
• melatonin suppression
• sleep
• variability

Acknowledgments

We would like to thank Jessica Riccardi for support with figure production.

Disclosure statement

SR, RV and CC declare current employment, and CS declares prior employment and current consulting work, with Delos Living LLC, a private sector and for-profit company. As part of their employment with Delos, each of them is a named co-inventor on at least one filed patent application related to indoor environments and well-being, some of which pertain specifically to lighting. EMM, AJKP and SWC have received research funding from Delos and Versalux. AJKP and SWC are co-founders and co-directors of Circadian Health Innovations PTY LTD. EMM and SWC have also received research funding from Beacon Lighting, and SWC has consulted for Dyson.

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Funding

The author(s) reported there is no funding associated with the work featured in this article.