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Inorganic light-emitting diodes – better known as LEDs – are ubiquitous in the modern era. Found in cell phones, televisions, computer screens, and a host of other electronic devices, LEDs emit short-wave, high-energy blue light, which has been linked to a wide range of harmful effects on health and sleep. Findings from a recent study suggest that organic LEDs (OLEDs), which produce less light in the blue-wave spectrum, have fewer harmful effects on human metabolism.

Light exposure is one of the primary regulators of the body’s circadian rhythms and plays key roles in sleep quantity and quality. For example, evidence indicates that afternoon exposure to blue light impairs the release of melatonin – the “sleepiness hormone” – in a dose-dependent manner. Similarly, use of LED-lit devices in the evening interferes with sleep by promoting alertness.

The cross-over study involved ten healthy males (average age, 25 years) who did not have sleep disorders. The participants were exposed to either LED, OLED, or dim light for four hours prior to going to sleep. The study investigators assessed the participants' sleep quality via polysomnography as well as the participants' self-assessment. The participants ate breakfast one hour after waking up, and the authors measured the participants' energy expenditure, fat oxidation, core body temperature, and melatonin levels for four hours (continuously) in a room with regular lighting. Each of the participants underwent all three lighting scenarios.

The investigators found that after OLED exposure, the participants' energy expenditure and core body temperature during sleep were lower than after LED exposure, but their fat oxidation was higher. In addition, the increase in fat oxidation following OLED exposure was associated with higher melatonin levels. Sleep quality did not differ markedly between the different lighting scenarios.

These findings suggest that evening OLED exposure elicits fewer harmful health effects than LED exposure, likely because OLEDs emit less blue light. Learn more about the effects of blue light in this clip featuring sleep expert Dr. Matthew Walker.

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