Differential effects of light wavelength in phase advancing the melatonin rhythm

Feb 14, 2004Journal of pineal research

Different light colors change the timing of melatonin rhythm in different ways

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Abstract

Shorter wavelengths of light (470-525 nm) may advance the saliva melatonin rhythm by approximately 40-65 minutes.

Longer wavelengths (595 nm and 660 nm) did not produce significant phase advances in melatonin onset.
Light exposure was administered via portable light-emitting diodes with a specific irradiance of 65 microW/cm².
A total of 42 volunteers participated in the study, with 15 individuals per condition across six conditions.
The study measured melatonin onset before and after light exposure to determine phase shifts.
Findings support the notion that the human circadian system is more responsive to shorter wavelengths of light.

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Shorter wavelength light has been shown to be more effective than longer wavelengths in suppressing nocturnal melatonin and phase delaying the melatonin rhythm. In the present study, different wavelengths of light were evaluated for their capacity to phase advance the saliva melatonin rhythm. Two long wavelengths, 595 nm (amber) and 660 nm (red) and three shorter wavelengths, 470 nm (blue), 497 nm (blue/green), and 525 nm (green) were compared with a no-light control condition. Light was administered via a portable light source comprising two light-emitting diodes per eye, with the irradiance of each diode set at 65 microW/cm(2). Forty-two volunteers participated in up to six conditions resulting in 15 per condition. For the active light conditions, a 2-hr light pulse was administered from 06:00 hr on two consecutive mornings. Half-hourly saliva samples were collected on the evening prior to the first light pulse and the evening following the second light pulse. The time of melatonin onset was calculated for each night and the difference was calculated as a measure of phase advance. The shorter wavelengths of 470, 495 and 525 nm showed the greatest melatonin onset advances ranging from approximately 40-65 min while the longer wavelengths produced no significant phase advance. These results strengthen earlier findings that the human circadian system is more sensitive to the short wavelengths of light than the longer wavelengths.

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Differential effects of light wavelength in phase advancing the melatonin rhythm

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