Blue light is a portion of the visible light spectrum with wavelengths roughly between 380 and 500 nanometers (nm), characterized by its shorter wavelengths and higher energy compared to other colors of light:
- the use of light-emitting electronic devices before bedtime may contribute to or exacerbate sleep problems (1)
- exposure to blue-wavelength light in particular from these devices may affect sleep by suppressing melatonin and causing neurophysiologic arousal
- melatonin acts as the hormonal signal for the onset of the biological night and has been conceptualized as the factor which “opens the sleep gate”
- environmental light can phase delay rhythms of melatonin and alertness when presented during nighttime hours
- blue light is considered as light with a short wavelength (2)
- the shorter the wavelength, the higher the energy
- has been shown blue light has more detrimental effects on the light receptor cell in comparison with green and white lights
- in the past, the only source for blue light was the sun; however, nowadays, there have been many sources, including laptops, digital TVs, and computers, the most important of which are smartphones and laptops
A Cochrane systematic review concluded (3):
- (i) There may be no short‐term advantages with using blue‐light filtering lenses to reduce visual fatigue with computer use, compared to non‐blue‐light filtering lenses.
- (ii) There is limited information about the potential effect(s) of blue‐light filtering lenses on visual acuity and the effects on sleep‐related measures are unclear. The existing evidence regarding these measures is inconclusive.
- (iii) None of the included studies investigated contrast sensitivity, colour discrimination, discomfort glare, macular health, serum melatonin levels or overall patient visual satisfaction; no conclusions could be drawn in relation to these measures.
- (iv) There is some evidence that harmful effects that may be related to using blue‐light filtering lenses include headache (1 study, 8%), increased depressive symptoms (1 study, 17%), lowered mood (1 study, 5%), and discomfort wearing the glasses (2 studies (combined), 22%), although similar adverse effects were also reported with non‐blue‐light filtering lenses and there were not enough data to accurately measure or determine possible harmful effects with certainty
A review concluded (2):
- due to factors such as increasing use of digital screens at night and urban light pollution, modern life is linked to significant interruptions in light-dark cycles
- blue light from digital screens is associated with a wide variety of problems ranging from macular degeneration, and cataracts to poor sleep, mental health problems and even increased risk for some cancers
Reference:
- Schechter A et al. Blocking nocturnal blue light for insomnia: A randomized controlled trial. J Psychiatr Res. 2018 Jan;96:196-202.
- Haghani M et al. Blue Light and Digital Screens Revisited: A New Look at Blue Light from the Vision Quality, Circadian Rhythm and Cognitive Functions Perspective. J Biomed Phys Eng. 2024 Jun 1;14(3):213-228.
- Singh S et al. Blue-light filtering spectacle lenses for visual performance, sleep, and macular health in adults. Cochrane Database Syst Rev. 2023 Aug 18;8(8):CD013244