Another scientific study has confirmed the positive effects of the light spectrum on sleep quality, visual comfort, well-being and daytime alertness.
Conducted by Prof Christian Cajochen and a team at the University of Basel, the study – entitled Effect of Daylight LED on Visual Comfort, Melatonin, Mood, Waking Performance and Sleep – was published in the Journal of Lighting and Research Technology on 24 March 2019.
There has been an increase in research activity on the relationship between light and human bio-function. It is well established that light is one of the strongest control factors for human circadian rhythms, such as the secretion of the sleep-promoting hormone melatonin. Thus, optimal lighting condition during daytime are crucial to prevent circadian rhythm disturbances which can lead to sleep disorders and other life-style related diseases.
Over the past 10 years, there have been related scientific studies in the fields of sleep, chronobiology, physiology, as well as the impact of light quality in elderly care.
According to Prof Cajochen’s research, LED light sources with the same measured correlated colour temperature (CCT) and intensity but different spectral output can have measurably different effects on human behaviour and physiology.
The research tested subjects’ visual comfort, circadian physiology, daytime alertness, mood, cognitive performance, and sleep after being exposed to both conventional LED light, and natural spectrum LED light for 49 hours in a laboratory setting.
It found that LED light sources with a spectrum close to natural sunlight produced better visual comfort, more alertness, and happier moods in the morning and evening among the test participants, compared to those exposed to conventional spectrum LEDs.
The study involved 15 young males who twice spent 49 hours in the laboratory under conventional-LED and then daylight-LED conditions. Despite different light spectra, the photopic lux and the correlated colour temperature of the lighting were the same for both LEDs. The colour rendering index and the melanopic strength were both higher for the daylight LED than the conventional LED, by 25.3 percent and 21 percent respectively.
The volunteers had better visual comfort, felt more alert and happier in the morning and evening under daylight LED than conventional LED, while the diurnal melatonin profile, psychomotor vigilance and working memory performance were not significantly different.