Abstract
The control of sleep/wakefulness is associated with the regulation of energy metabolism. The present experiment was designed to assess the effect of nocturnal blue light exposure on the control of sleep/wakefulness and energy metabolism until next noon. In a balanced cross-over design, nine young male subjects sitting in a room-size metabolic chamber were exposed either to blue LEDs or to no light for 2 h in the evening. Wavelength of monochromatic LEDs was 465 nm and its intensity was 12.1 μW/cm(2). During sleep, sleep architecture and alpha and delta power of EEG were similar in the two experimental conditions. However, the following morning, when subjects were instructed to stay awake in a sitting position, duration judged as sleep at stages 1 and 2 was longer for subjects who received than for those who received no light exposure. Energy metabolism during sleep was not affected by evening blue light exposure, but the next morning energy expenditure, oxygen consumption, carbon dioxide production and the thermic effect of breakfast were significantly lower in subjects who received blue light exposure than in those who received no light exposure. Exposure to low intensity blue light in the evening, which does not affect sleep architecture and energy metabolism during sleep, elicits drowsiness and suppression of energy metabolism the following morning.
Highlights
The artificial light environment has experienced a dramatic change during the last decade
There was no significant difference in sleep architecture during bedtime
There are no significant differences in energy metabolism during the dark adaptation, the light exposure and the sleep periods (Fig. 3)
Summary
The artificial light environment has experienced a dramatic change during the last decade. The use of light-emitting diodes (LED)-based lighting has been increasing since the innovation of high-brightness blue LEDs in mid-1990s. Supported by energy policy in each country, it is predicted to replace incandescent bulbs and fluorescent lamps to provide an energy-efficient and long-lasting option for everyday use in many areas of the globe. LED-based white light consists of either blue LEDs with yellow phosphors or a combination of red, green and blue LEDs. Compared with incandescent bulbs, fluorescent lamps and natural light, the LED-based white light is extremely enriched with a blue light component [1]. The LEDs are used for visual displays terminals (VDT), and VDTs are standard equipment both at work and at home in the front of computers, TVs, smart phones and games in industrialized societies
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