Chromatic and spectral quality of lighting for self-dependent elderly people well-being: a case study

Natural and artificial light (quantity, duration and time, distribution and direction, spectra along with color temperature) influences non-visual processes and plays a fundamental role in physical (heart rate, body temperature, blood pressure), mental (cognitive performances, subjective alertness, short-term memory) and behavioural regulations (mood, appetite, wakefulness/sleep), by setting the principal biological clock to the day/night cycles. In domestic dwellings, the circadian system of elderly people can be disrupted both due to the limited availability of natural light in interiors and to the modification of the aged eyes and the yellowing of the crystalline lenses with reductions of the chromatic quality of light reaching the retina. This paper focuses on this phenomena by presenting a research conducted through a field study in a real domestic environment. By investigating the availability and impact of the natural light experienced by elderly people, the paper would describe the methodology and the results achieved. Measurements show that, in interiors, elderly people experience low levels of natural light which are generally not sufficient to activate non image forming responses and so to synchronize their circadian clock during the winter (colder and more sedentary) season.