"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:
Imbalance of mitochondria dynamics in the retina by exposure to blue light:
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:
Displays and sleep
Digital display use in the evening leads to insomnia and later sleep:
Higher social jetlag is a risk factor for prosocial behavior problems in adolescents:
Digital display use and sleep problems:
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:
Great collection and summary of negative health effects of flicker:
Short-sightedness
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):
Serious consequences of the myopia epidemic: