Abstract
Current research on the relationship between daylight and well-being has shown that access to daylight plays a relevant role both in terms of light perception and with respect to physiological mechanisms not directly related to vision. The aim of this paper is to analyze changes in reported light perception and in physiological responses, represented in this case by the skin temperature of research participants (n = 16) across three seasons (winter, spring and summer seasons) in a temperate, mid-latitude location, Karlsruhe, in southern Germany (49°N, 8.5°E). Sessions have been held in thermally stable rooms of a climate chamber, with daylight exposure to two opposing solar orientations of the glazed façade, namely equatorial and non-equatorial orientations, over 5-h morning sessions. Differences in light perception as well as changes in physiology have been observed. Results showed an increased sensitivity of the individuals in terms of light perception to changes in daylight in winter while such sensitivity dropped in spring and summer, with greater daylight availability and diminished lighting variability during sessions. Due to the intrinsic relationship between light perception and circadian entrainment, the same was verified for changes in skin temperature, which were also found to be significantly related to daylight availability. Seasonal influence suggests that variability of brightness and correlated color temperature (CCT) of natural light can affect both psychological and physiological patterns in humans.
Highlights
Our circadian rhythm is controlled by the activation of melatonin production with concurrent suppression of cortisol during the night, followed by a reversal of this mechanism during the day, cyclically interchanging latent and active states, commonly known as the sleep/wake cycle, within ∼24 h or so
Results are presented in two sections, namely subjective daylight judgment and physiological changes observed in skin temperature of participants for seasonal variations of light exposure
Our findings suggest that mainly when users of indoor spaces have to struggle with limited light requirements, they become more sensitive to minor changes in available light and the circadian factor is more affected and activated
Summary
Our circadian rhythm is controlled by the activation of melatonin production with concurrent suppression of cortisol during the night, followed by a reversal of this mechanism during the day, cyclically interchanging latent and active states, commonly known as the sleep/wake cycle, within ∼24 h or so. The adaptation of our species to natural rhythms over time, as regards the mammalian hypothalamus, created a perfect synchronization to the diurnal and nocturnal periods (Kudielka and Kirschbaum, 2003) Such synchronization is season dependent in connection to the availability of daylight, with a production of melatonin taking place during longer periods in winter than in summer (Mead, 2008). In many buildings the reduced access to natural light lead to an increase and even to Seasonal Effects of Daylight Conditions a dependency on artificial lighting of its occupants in order to perform their activities indoors Under such conditions, the circadian rhythm gets seriously disrupted and consequences are noticed in terms of health and wellbeing. Mood and mental health disorders can be associated to disruptions of the circadian rhythms (Walker et al, 2020) as well as alterations in cognitive abilities with related impacts on health and behavior (Sharma et al, 2016)
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