"Blue light" and its impact
In general terms, blue light is a stressor: on the positive side, it wakes us up and prepares us for the activities of the day; on the negative side, it can deplete our reserves and cause harm, or simply keep us awake and reduce the efficiency of sleep and recovery.
In natural light, blue light stress is always balanced by the presence of red and near-infrared (long-wavelength) light, which generally has the opposite effect. In modern electric lighting, blue light is frequently present in disproportionate quantities, at the wrong time of the day, and without any of the long wavelengths to counterbalance its physiological ramifications. Therefore, comparing blue light exposure in isolation from its context is not appropriate. In other words, blue light from sunlight cannot be directly compared to the same amount of blue light exposure from indoor electric light.
Note: the term "blue light" is somewhat imprecise, since color is a perceptual interpretation, not a property of light itself. Therefore, the term short-wavelength visible light (the short end of the spectrum is violet and blue light) is often used instead.
Blue light as a stressor
Blue light restricts cell respiration and energy production:
Kaynezhad et al. (2022) Near infrared spectroscopy reveals instability in retinal mitochondrial metabolism and haemodynamics with blue light exposure at environmental levels. Journal of Biophotonics, 15.
Imbalance of mitochondria dynamics in the retina by exposure to blue light:
Wang et al. (2023) Long-term blue light exposure impairs mitochondrial dynamics in the retina in light-induced retinal degeneration in vivo and in vitro. Journal of Photochemistry and Photobiology B: Biology, 112654.
Chronic exposure to white-LED light may also cause retinal harm at domestic levels:
Increased oxidative stress, inflammation and cell death in tissues in the front of the eye by blue light:
Mechanisms of photochemical harm and why (at least one reason, why... aside from the lack of long wavelengths) electric light supplementation against seasonal affective disorder can be harmful:
Photodamage by blue LED light causes mitochondrial dynamics deregulation in the retinal pigment epithelium (which supplies nutrients to and cleans up waste from the retina), with potential contribution to age-related macular degeneration:
Alaimo et al. (2019) Toxicity of blue led light and A2E is associated to mitochondrial dynamics impairment in ARPE-19 cells: implications for age-related macular degeneration. Archives of Toxicology, 93.
The mainstream in displays, after decades of denial, is finally starting to acknowledge some of the health problems with blue light from screens. Their proposed mitigation measures are still band-aids at best, as they do not take into account the interactive nature of the physiological effects of various frequencies:
Displays and sleep
Digital display use in the evening leads to insomnia and later sleep:
Fossum et al. (2014) The association between use of electronic media in bed before going to sleep and insomnia symptoms, daytime sleepiness, morningness, and chronotype. Behavioral sleep medicine, 12.
Blue light from displays in the last hour of the day: reduced melatonin secretion and evening sleepiness, later timing of the circadian clock, and reduced alertness the next morning:
These effects are mainly melanopsin-dependent (at a given illumination level, the proportion of power in the blue-green part of the spectrum matters the most, regarding sleep):
Circadian effects of blue light are most pronounced at the center of the visual field (projected to the macula of the retina). Therefore, computer displays are the most efficient lighting application to achieve such effects (for good or for bad):
Higher social jetlag is a risk factor for prosocial behavior problems in adolescents:
Software solutions insuﬃcient against sleep disruption by blue light from displays:
A short summary of some of the negative effects of display use on youth by the French National Academy of Medicine:
Displays and eye strain
Public health perspective: a review on blue light harm and digital eye strain in children:
Positive effects of filtering blue light: increased acuity with special regards to dry eye patients
A key mechanism through which flicker disrupts eye movement planning and thus decreases work performance:
The worse the flicker, the greater the resulting negative effect on cognitive performance, arousal, and associated brain and pupil functioning:
Great collection and discussion of negative health effects of flicker (these sources also concern with software-based causes of flicker, which are beyond the scope of the display itself; however, all issues with flicker from the backlight can be solved by a continuous backlight source, as in Pixun):
A potential mechanism linking blue light, pain, and photosensitivity:
Incomplete light spectrum is mechanistically implicated in short-sightedness:
How blue and red light together lead to normal development of good focus:
Red light acts against the development of short-sightedness:
While the exact contribution of various mechanisms is an open question, time spent outdoors helps prevent short-sightedness:
Even broader spectrum LED helps with myopia (while, for many reasons as shown here with other studies, it certainly cannot compete with natural light):
Muralidharan et al. (2022) Recovery From Form-Deprivation Myopia in Chicks Is Dependent Upon the Fullness and Correlated Color Temperature of the Light Spectrum. Investigative Ophthalmology & Visual Science, 63.
Serious consequences of the myopia epidemic: