Prolonged exposure to light during the night can have negative consequences for human health. But now researchers from Japan have identified a new type of light that has less impact on physiological changes in sleep.
In a study published in Scientific Reports in June 2021, researchers from Tsukuba University compared the effects of light-emitting diodes (LEDs), which are widely used due to their energy-saving properties, with organic light-emitting diodes (OLEDs) on physical processes that take place during sleep.
Polychromatic white LEDs emit a large amount of blue light, which has been linked to many negative health effects, including metabolic health. In contrast, OLEDs emit polychromatic white light that contains less blue light. However, the effects of LED and OLED exposure at night were not compared in terms of changes in energy metabolism during sleep, which researchers at Tsukuba University wanted to address.
“The energy metabolism is an important physiological process that is changed by exposure to light,” says the lead author of the study, Professor Kumpei Tokuyama. “We hypothesized that OLED exposure has a smaller impact on sleep architecture and energy metabolism compared to LEDs, similar to that of low light.”
To test this hypothesis, the researchers exposed 10 male participants to LED, OLED, or low light for 4 hours before sleeping in a metabolic chamber. The researchers then measured energy expenditure, core body temperature, fat oxidation, and 6-sulfatoxymelatonin – a measure of melatonin levels – during sleep. The participants had not recently traveled or worked in shifts.
“The results confirmed part of our hypothesis,” explains Professor Tokuyama. “Although no impact on sleep architecture was observed, energy expenditure and core body temperature during sleep were significantly reduced after OLED exposure. In addition, fat oxidation during sleep was significantly lower after LED exposure compared to OLED. “
In addition, fat oxidation during sleep was positively correlated with 6-sulfatoxymelatonin levels after OLED exposure, suggesting that the effect of melatonin activity on energy metabolism varies depending on the type of light exposure.
“Therefore, night light exposure is related to fat oxidation and body temperature during sleep. Our results suggest that certain types of light exposure, along with other physiological changes, can affect weight gain, ”says Professor Tokuyama.
Many occupations and activities involve exposure to artificial light before bed. New insights into the effects of different types of light on physical processes can facilitate the selection of alternative light sources in order to mitigate the negative effects of light exposure at night. In addition, these findings expand our knowledge of the role of light in the energy metabolism during sleep.
Reference: Ishihara A, Park I, Suzuki Y, et al. Metabolic reactions to polychromatic LED and OLED light at night. Sci Rep. 2021; 11 (1): 12402. doi: 10.1038 / s41598-021-91828-6
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