Circadian rhythms are physical, mental, and behavioral changes that follow a daily cycle. They respond primarily to light and darkness in an organism's environment. Natural factors within the body produce circadian rhythms. However, signals from the environment also affect them. The main cue influencing circadian rhythms is daylight. This light can turn on or turn off genes that control the molecular structure of biological clocks. Changing the light-dark cycles can speed up, slow down, or reset biological clocks as well as circadian rhythms. Circadian rhythms can influence sleep-wake cycles, hormone release, eating habits and digestion, body temperature, and other important bodily functions. Biological clocks that run fast or slow can result in disrupted or abnormal circadian rhythms. Irregular rhythms have been linked to various chronic health conditions, such as sleep disorders, obesity, diabetes, depression, bipolar disorder, and seasonal affective disorder.
As we outlined above, exposure to light affects directly biological and mental function of human body. In other words, affects directly mental and physical performans of human body
While we are discussing the performans of the lighting equipment we generally focus on energy efficiency and connctivity functions. But it is clear that there is much more important parameter that we need to focus. It is the efficiency of mental performans of the people due to light exposure.