Abstract
Light exposure at night has various implications for human health, but little is known about its effects on energy metabolism during subsequent sleep. We investigated the effects of polychromatic white light using conventional light-emitting diodes (LED) and an alternative light source, organic light-emitting diodes (OLED), producing reduced spectral content in the short wavelength of blue light (455 nm). Ten male participants were exposed to either LED, OLED (1000 lx), or dim (< 10 lx) light for 4 h before sleep in a metabolic chamber. Following OLED exposure, energy expenditure and core body temperature during sleep were significantly decreased (p < 0.001). Fat oxidation during sleep was significantly reduced (p = 0.001) after the exposure to LED compared with OLED. Following exposure to OLED, fat oxidation positively correlated with the 6-sulfatoxymelatonin levels, suggesting that the role of melatonin in lipolysis differs depending on the light. These findings advance our knowledge regarding the role of light in energy metabolism during sleep and provide a potential alternative to mitigate the negative consequences of light exposure at night.
Highlights
Artificial light at night has transformed the lives of human beings, enabling a wide array of evening activities
Respiratory quotient (RQ), and fat oxidation were analyzed separately according to sleep and wake periods (Fig. 1, Supplementary Fig. 3)
There was a difference in mean energy expenditure (F2,138 = 6.1, p = 0.003) with a significant post hoc comparison between Organic light-emitting diodes (OLED) and dim light (p < 0.001; Fig. 1e)
Summary
Artificial light at night has transformed the lives of human beings, enabling a wide array of evening activities. The difference in the spectral composition between LEDs and OLEDs is crucial because melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs) are most sensitive to short wavelength of blue light[10] These non-image-forming photoreceptors transmit their signals to the suprachiasmatic nucleus in the anterior hypothalamus, thereby entraining the circadian rhythm, and further project information to the pineal gland where they affect melatonin s ynthesis[11]. The rapid development and increase in the number of studies of artificial light at night have provided insight into its important role in metabolic health. The results of both animal model and epidemiologic. The impact of light exposure at night on energy metabolism during sleep remains unknown
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