Protecting the Melatonin Rhythm through Circadian Healthy Light Exposure

Abstract

Currently, in developed countries, nights are excessively illuminated (light at night), whereas daytime is mainly spent indoors, and thus people are exposed to much lower light intensities than under natural conditions. In spite of the positive impact of artificial light, we pay a price for the easy access to light during the night: disorganization of our circadian system or chronodisruption (CD), including perturbations in melatonin rhythm. Epidemiological studies show that CD is associated with an increased incidence of diabetes, obesity, heart disease, cognitive and affective impairment, premature aging and some types of cancer. Knowledge of retinal photoreceptors and the discovery of melanopsin in some ganglion cells demonstrate that light intensity, timing and spectrum must be considered to keep the biological clock properly entrained. Importantly, not all wavelengths of light are equally chronodisrupting. Blue light, which is particularly beneficial during the daytime, seems to be more disruptive at night, and induces the strongest melatonin inhibition. Nocturnal blue light exposure is currently increasing, due to the proliferation of energy-efficient lighting (LEDs) and electronic devices. Thus, the development of lighting systems that preserve the melatonin rhythm could reduce the health risks induced by chronodisruption. This review addresses the state of the art regarding the crosstalk between light and the circadian system.

Depressive disorders: Processes leading to neurogeneration and potential novel treatments

“…In those patients who spend less time in darkness because of late bedtime, being up at night, or early wakening the presence of light would suppress melatonin synthesis (Claustrat et al, 2005;Zawilska et al, 2009). It is clearly essential that exposure to light occurs in a healthy circadian way in order to maintain normal body rhythms including a normal nocturnal melatonin rise (Bonmati-Carrion et al, 2014).…”

Ground-based hyperspectral analysis of the urban nightscape

“…Although there are still considerable uncertainties in this field, the basic mechanisms of the interaction of artificial light at night with the human physiology are progressively being unveiled (see the review in Bonmati-Carrion et al, 2014). A comprehensive model describing the effects of the nocturnal exposure to light on the production of the hormone melatonin (MLT) has been proposed by Rea et al (2005Rea et al ( , 2010Rea et al ( , 2012.…”

Synchrony and desynchrony in circadian clocks: impacts on learning and memory

“…Moreover, technological advances have resulted in increased human exposure to artificial light at night, particularly blue wavelengths that most affect the circadian clock, compounding the problems of circadian disorders in modern society (for review, see Bonmati-Carrion et al 2014;Stevens and Zhu 2015). Consequently, identifying methods to maintain circadian rhythms or minimize circadian misalignment are necessary both at home and the workplace.…”