What is the Origin of Non-Circadian Light Impact?

This concept originates from chronobiology and photobiology, recognizing that the human eye contains intrinsically photosensitive retinal ganglion cells (ipRGCs) that relay light information to the SCN, influencing far more than just vision. It highlights the subtle yet profound influence of modern, artificial light environments. The term defines a functional disruption of the central clock.

What is the Mechanism of Non-Circadian Light Impact?

The non-circadian impact operates by stimulating the ipRGCs, which transmit signals to the SCN, potentially shifting the phase of the central clock or suppressing the nocturnal rise of melatonin. For example, exposure to short-wavelength (blue) light after sunset can delay the onset of sleep and disrupt the nocturnal restorative processes that govern Growth Hormone release and glucose metabolism. This disruption compromises the precise hormonal orchestration of the sleep-wake cycle.

Non-Circadian Light Impact ∞ Area

Non-Circadian Light Impact

Meaning

The physiological effect of light exposure that occurs outside the parameters typically used by the suprachiasmatic nucleus (SCN) to set the primary 24-hour circadian rhythm, such as specific wavelengths or intensities encountered during the subjective night. This impact can significantly disrupt hormonal balance, including melatonin secretion and cortisol’s diurnal pattern, even when the timing is not classically considered ‘late night.’ It encompasses light that is insufficient or inappropriately timed to support healthy entrainment.