Summary
Light sensitivity of the melanopsin system is significantly higher in winter than summer due to reduced daytime light exposure, meaning studies conducted in winter may overestimate circadian and sleep effects of evening light. Lighting researchers and designers should account for seasonal light history when interpreting or applying findings from circadian lighting studies, and reporting season should become a standard practice.
Key Findings
- Light sensitivity to evening light was reduced in summer compared to winter in a dataset of 72 participants, suggesting seasonal modulation of the melanopsin system.
- A systematic review of the literature found that more sleep and circadian studies were conducted in winter than in summer, introducing a potential bias toward larger NIF effect sizes.
- Reporting of season or individual light history is not currently standard practice in sleep and circadian research, undermining reproducibility.
- The laboratory protocol used melanopic irradiance levels below 90 lx across four light levels, and retrospective analyses revealed seasonal differences in circadian and sleep outcomes.
Categories
Sleep & Circadian Health: Investigates how seasonal variation in light history modulates melanopsin system sensitivity and its effects on circadian rhythms and sleep.
The Science of Light: Examines non-image forming (NIF) effects of evening light and melanopic irradiance across seasons, with implications for lighting standards and research reproducibility.
Author(s)
I Schöllhorn, O Stefani, C Blume, C Cajochen
Publication Year
2023
Number of Citations
1
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The Science of Light
- Phototransduction by retinal ganglion cells that set the circadian clock
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- The mammalian circadian timing system: organization and coordination of central and peripheral clocks
- Diminished pupillary light reflex at high irradiances in melanopsin-knockout mice
- Melanopsin is required for non-image-forming photic responses in blind mice