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bioRxiv · 10.1101/2024.10.10.617409

Lack of evidence for the contribution of cone photoreceptors to human melatonin suppression and alerting response to light at night

Fazlali, F.·Lazar, R.·Yahya, F.·Epple, C.·Spitschan, M.·Stefani, O.·Cajochen, C.
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Abstract

Light exposure at night can suppress melatonin production and increase alertness, primarily through the action of melanopsin-containing intrinsically photosensitive retinal ganglion cells (ipRGCs). This study investigated whether cone photoreceptors also influence melatonin suppression and subjective alertness using non-visual metameric light emitted from a display. Forty-eight participants with normal trichromatic vision were exposed to three lighting conditions: a baseline (9 lxmEDI), constant background (149 lxmEDI), and cone-modulated flickering light targeting different cone combinations and post-receptoral channels (149 lxmEDI) for 2 hours after their habitual bedtime. Salivary melatonin levels and subjective alertness were measured throughout a 9-h protocol. Bayesian analysis showed that cone-modulated flickering light did not significantly affect melatonin suppression or alertness, providing evidence against the hypothesis that cone photoreceptors contribute to these non-visual effects of light. In conclusion, our results suggest cone photoreceptors do not play a measurable role in lights effects on melatonin suppression and subjective alertness at night.

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Fazlali, F., Lazar, R., Yahya, F., Epple, C., Spitschan, M., Stefani, O., Cajochen, C.. 2024-10-14. Lack of evidence for the contribution of cone photoreceptors to human melatonin suppression and alerting response to light at night. https://doi.org/10.1101/2024.10.10.617409

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