Ill-lighting syndrome: prevalence in shift-work personnel in the anaesthesiology and intensive care department of three Italian hospitals

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 [1].

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 [2].

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 [7].

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 [8].

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 [9]. 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.

The degree of stress reported were: Intensive Care, mean stress = 55.8%, high stress = 34.6%; Operating Theatres: mean stress = 51.5%, high stress = 33.8%).

Comparing the number of hours worked per week by the doctors and nurses, it emerged that, although the former group worked longer hours, the latter tended to report higher levels of stress (Figure 2, 3); the doctors who worked from 46 to 50 hours per week reported stress levels of 57% and the nurses who worked from 37 to 45 hours per week reported stress levels of 46%, a higher amount of stress per hour. (Figure 4). The physicians declared a far higher capacity to influence their work flow (autonomy) than the nurses (62 vs. 38), with a statistical significance of p = 0.01 (Table 1).

Among the familial responsibilities, those other than the care of elderly parents or children, such as the care of a pet, in particular a dog, had a tendency to elevate stress levels (Figure 5), which were comparable to those reported by workers who were discomforted by the artificial light in the operating theatres and Intensive Care departments (Figure 6).

In order to verify the hypothesis that artificial light affects workers' mood, we carried out a logistic regression analysis using the stress index as the dependant variable (Figure 7), and how independent variables the types of exposure with the horizontal luminance (lux) (< 700 lux, between 1000–1500 lux, > 1500 lux), weekly hours of work, professional qualification (type of job). It can be observed that the percentage of high stress diminishes as the exposure to lux increases, although this reduction was not found to be statistically significant (Table 2, Figure 8).

The influence of light on human health, its role in regulation of the circadian rhythm, and its therapeutic applications in seasonal mood disorders have been described in numerous articles [2, 6, 14]. In studies on shift workers who experience overexposure to artificial light at night, an alteration in normal psychological and circadian behavioural rhythms have been revealed [3]. In our study we measured the subjective emotional discomfort and its correlation with environmental stimuli in the workplace, in particular the level of illumination.

In 2001, Veich and McColl disputed the validity of an effect of exposure to artificial light generated by fluorescent lights on development and psychological processes. More recently, the role of light in mood regulation of the circadian cycle and its psychological effects [1, 3] has been the subject of rigorous studies aimed at finding correlations between the impact of light and colour on mood [6].

Küller explored the effect of illumination on workers subject to variations in stimuli in relation to their collocation in different seasons and latitudes. He found that the perception of light as anomalous affected the mood of the population, but this effect was not confirmed when the illumination was measured in objective terms. In our study we measured subjective emotional discomfort (stress) and its correlation with environmental discomfort factors in the workplace in particular the lighting level. The singularity of our study, focussed on identifying states of emotional disturbance in the Emergency Department personnel of three Italian hospitals, is the homogeneity of the sample. This consisted of public health workers who operate under the same environmental conditions; they carry out their duties in operating theatres and Intensive Care units, and are confined to closed, air-conditioned environments with a lack of natural light, which is substituted by the artificial variety in the form of fluorescent lights. Their clothing, their posture, the procedures they carry out (anaesthesiological assistance in a variety of surgical operations on critical patients), and the structural characteristics of the environments are all similar, differing only in the level of luminance measured.

Data on the levels of illumination in the workplace were obtained by measurements carried out according to European regulations, which indicate the quantitative and qualitative parameters of illumination in the workplace necessary to provide the workers with adequate visual comfort and performance. The subjects in our study manifested a medium-high level of stress, which, confirms the findings by Küller, showing no correlation with the objective ambient light measured. Also analogous to Küller's study, a tendency to increased stress was found in the subjects who reported a perceived light-caused discomfort, in terms of excessive glare or darkness.

Regarding the other items, it was observed that although the doctors work longer hours, the nurses reported a higher level of stress. It can be hypothesized that this is linked to the fact that the doctors have more autonomy at work, having decision-making powers that the nurses do not. Another characteristic of our survey is taking into consideration stress from familial conditions. The level of stress in our workers was found to be influenced by working and familial conditions, rather than ambient lighting stimuli.

Limitations of this study are due to small size of the sample and the need to improve the questionnaires reliability and validity. In the future we want to retest the same sample.

Despite the limitations of the study, we cannot share in the enthusiasm of some authors, and the electronics industry, regarding the effects on well-being correlated to the use of fluorescent lamps [15]. The level of stress in our workers was found to be influenced by familial and working conditions, irrespective of ambient lighting stimuli.