Study indicates that light color may not have an impact on sleep

Researchers from the University of Basel and the Technical University of Munich conducted a recent study that raises the possibility that light color has little effect on sleep or the body’s internal clock. The study was released in the scholarly journal “Nature Human Behaviour.”

The goal of the research project was to find out how various light colors affected sleep and the body’s internal clock. For an hour in the late evening, the researchers subjected 16 healthy volunteers to either a blue or yellow light stimulus, with white light serving as the control condition.

The purpose of the light stimuli was to precisely and selectively activate the retina’s color-sensitive cones. The three conditions did not alter the stimulation of the ganglion cells that are sensitive to light. Thus, variations in the light’s impact could be directly linked to the cones’ individual stimulation and, in the end, the light’s color.

Next, the researchers measured the duration of the volunteers’ initial nighttime sleep as well as the depth of their sleep. They also tested their reaction time, which gets worse as people get sleepier.

The study’s first author, Christine Blume, states that  “We found no evidence that the variation of light colour along a blue-yellow dimension plays a relevant role for the human internal clock or sleep, “Rather, our results support the findings of many other studies that the light-sensitive ganglion cells are most important for the human internal clock.”

One of the study’s researchers, Manuel Spitschan, believes the conclusions represent a significant advancement in the application of fundamental research. “Our findings show that it is probably most important to take into account the effect of light on the light-sensitive ganglion cells when planning and designing lighting. The cones and therefore the colour play a very subordinate role.”

If the parameters are altered and the length of the light exposure is increased or occurs at a different time, more research is required to ascertain whether the color of the light has no effect on sleep.