Lighting characteristics during the polar day and their impact on changes in melatonin secretion

Abstract

People traveling between climate zones can be exposed to extreme environmental stimuli which significantly differ from their place of habitual residence. A move from the temperate climate of Central Europe to the subpolar climate of northern Europe means exposure to great changes in two climate parameters: lighting and biothermal characteristics. The sudden change of solar radiation, temperature, wind and humidity, force the organism to undergo intensive adaptation processes. While the change in lighting conditions involves a diurnal rhythm adaptation of the physiological clock (regulated by the hormone melatonin), the change of biothermal factors (represented by UTCI) produce additional stress on the strongly loaded human organism. The field experiment was carried out in Poland and Norway so the impact of the selected radiation stimuli on melatonin production could be carried out in conditions of natural constant lighting. The paper presents the results of the preliminary analysis of our research conducted from 22 May to 12 June 2011. The distribution of daily outdoor photosynthetically active radiation (PAR) intensity, which is a spectral distribution of solar visible radiation in selected times of the day were analyzed. Lighting conditions surrounding each subject (doses of reached energy of visible solar radiation and illumination intensity) were examined as well. Additional adaptation stress caused by different biothermal conditions (expressed by UTCI index) was also taken into consideration. Diurnal melatonin concentrations were determined in saliva samples.