Effects mediated by melatonin and cortisol of artificial light and noise, alone and in combination, on sleep and health

As an integral part of human chronobiology, the circadian system plays a crucial role in regulating key biological functions, including sleep and the intricate hormonal rhythms of melatonin (MLT) and cortisol (CORT). Scholars have increasingly recognized environmental stressors as significant contributors to disturbed sleep patterns. Albeit vigorously discussed individually, the literature lacks comprehensive insights into the synergistic effect of artificial light at night (ALAN) and noise. The aim of this review is to look into the intricate interplay of the ALAN effects on sleep architecture, the modulation of circadian function, and how this influences homeostatic sleep. Furthermore, ALAN suppresses MLT secretion, which is most pronounced in response to short wavelengths of light. In addition, this review will demonstrate how exposure to noise during sleep elevates CORT and noradrenaline levels, which contributes to stress-related diseases and sleep disturbances. ALAN and noise, persistently emitted into the environment, share intrinsic mechanisms with comparable characteristics. Therefore, understanding their combined impact has become increasingly urgent. Pre-sleep exposure to both ALAN and noise acts as a potent stressor, with the potential to disrupt sleep patterns. Interestingly, during sleep, noise emerges as the predominant influence on sleep quality. Moreover, these stressors often synergize and amplify one another’s adverse effects. Thus, limiting their exposure is crucial for cultivating a sustainable environment conducive to quality sleep and overall well-being.