Light is one of the most important factors in our interaction with the environment; it is indispensable to visual function and neuroendocrine regulation, and it is essential to our emotional perception and evaluation of the environment. Previous studies have demonstrated its effects on the psyche and also its therapeutic role: Berson, in 2002, documented the existence of a retinal photoreceptor linked to the supra-chiasmatic nucleus. This receptor has been ascribed a role in the transmission of neuronal transmission arising from light stimuli to the pineal gland, seat of the biological clock which presides over the regulation of the circadian system via the retinal hypothalamic pathway .
Control of the biological clock and the release of several important hormones (among which: cortisol, the stress hormone, and melatonin, the sleep hormone) are governed by the alternation of light and dark. Thus, exposure to light has important repercussions on human health and behaviour. A role in the regulation of the sleep/waking pattern, mood, body temperature and physical and cognitive performance has been attributed to daily and seasonal variations in light .
Recent studies have focussed on the effects of prolonged anomalous exposure to artificial light, both in outdoor and indoor environments, on alterations in the principal neuroendocrine mediators and on potential pathological effects such as: increased of risk of carcinogenesis, metabolic disorders (in particular obesity and diabetes), cardiovascular disease, acceleration of the aging process and alterations in regulation of the immune system [3, 4]. Many other studies have examined the emotional value of light and its role in the treatment of mood disturbances [5, 6].
Regarding work-related diseases, studies have been carried out on shift workers exposed to alterations in the normal day/night pattern, and thus to abnormal levels of intense light stimuli in the time usually reserved for sleep .
Does the so-called ill-lighting syndrome exist?
Begeman identifies the aetiology as an insufficient exposure to indoor light, with repercussions on workers' health and performance .
As recent research has demonstrated the physical characteristics of light act differently in determining visual and circadian photobiological functions of the retina.
The circadian system does not respond to the patterns of quantity, spectrum, distribution, time or duration of exposure to light which determine visual performance, but to the global sum of these criteria which penetrates the retina . So it was necessary to study the characteristics of the spaces where examined workers operate. The anaesthesiologists and nurses employed in the operating theatres and Intensive Departments are shift workers that operate for prolonged exposure under fluorescent lighting. The aim of this study is to investigate if this job condition can affect the health workers and to identify signs and symptoms of an emotional discomfort (stress), that form part of an ill-lighting syndrome.