52|CUADERNOS The influence of lighting in health Since the beginning of time, light has been associated to life. Recent studies show the importance of light on health, specially since it now has a more relevant role than in primitive days: lighting in the absence of natural light. In the health sphere, the appropriate use of lighting has an effect on sleeping patterns, in the recovery time of hospitalized patients and in the state of mind of people that have to undergo medical procedures. Light regulates the circadian cycle (or biological cycle) in humans by triggering hormones that activate or relax the body. As the sun rises, the increase in natural light causes the body to produce cortisol which activates body functions. As the sun sets, decreasing levels of light and softer tones cause the body to produce melatonin, a hormone that relaxes the body and decreases body functions. Sleep patterns are regulated by the circadian cycles. When the body secretes a larger quantity of cortisol, under natural conditions, we wake up and we begin our daily activities. The opposite happens when melatonin increases. The body relaxes and activity decreases resulting in sleep. An alteration of the circadian cycles results in changes in the sleeping patterns which could cause health problems. In the northern countries, where natural light is affected by the seasons (more light in summer and less in winter) there is an increase of sleep problems in people. Lighting (natural or artificial) is an important factor in the proper functioning of this cycle. There is not much we can do to modify natural light, but we can work on the artificial lighting we have at home, working place, hospitals, schools, etc. Dynamic lighting is the key for those spaces where we spend many hours. Thanks to the new lighting technologies based on LED and control systems, we can alter, not only the levels of lighting, but also its temperature and color simulating the cycle of day light. In this way we can improve people’s well being, shorten their recovery from illness and increase their productivity. Light and hospitals Hospitals, just as other buildings, need artificial lighting. Besides taking care of the energy efficience of the installations, which can be done with LEDs and management and control systems, the well being of the patients and workers has to be considered. Extended stay patients require special attenion.