High mEDI in daytime lighting increased daytime alertness, improved circadian functioning and improved sleep
The results of laboratory observations confirmed that increasing the intensity of illumination and adjusting the spectral composition of light during the day to resemble sunlight (high mEDI) increased stimulation of ipRGC photoreceptors (= intrinsically photosensitive retinal ganglion cells) and thereby promoted alertness, circadian rhythm and good sleep. Optimal lighting conditions can also increase heart rate, alleviate seasonal and non-seasonal depression, affect thermoregulation and brain activity as measured by electroencephalogram (EEG).
The CIE states that increased exposure to natural daylight is associated with better health and well-being. The CIE also recommends refraining from limiting daylight indoors and supplementing it with full-spectrum lighting in areas where natural light is scarce.
Reducing luminance and light emission in sensitive spectral regions in the evening and night-time hours (low mEDI) facilitated sleep initiation and consolidation.
According to research, light in the evening and at night disrupts sleep and causes an acute suppression of the release of the hormone melatonin. This can lead to disrupted circadian rhythms, fatigue, increased risk of health problems, stress and mood disorders. The CIE recommends adjusting melanopsin-based photoreception to optimise non-image forming responses by using high melanopic EDI during the day and low melanopic EDI in the evening and at night.
Measurement precision and melanopic EDI lux.
The latest version of the CIE statement (2024) adds precise parameters for light exposure in accordance with the biological needs of the organism, recommending a minimum daily exposure limit of 250 melanopic EDI lux, a maximum exposure of 10 EDI lux in the evening for three hours before bedtime and a maximum exposure of 1 EDI lux overnight during sleep. The CIE has now found that there are interconnections between photoreceptors, rather than a strict division between visual and non-visual effects, and therefore recommends that their functions should not be treated separately.
At the same time, the CIE recommends that the properties of light should no longer only be measured on a comparative plane, i.e., horizontally on the table top, but vertically, because that is the way light enters the eye of the biological recipient and affects the circadian rhythm.
