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Artificial light at night can have negative effects on human wellbeing and health. It can disrupt circadian rhythms, interfere with sleep, and participate in the progress of civilisation diseases. The aim of the present study was to explore if dim artificial light during the entire night (ALAN) can affect melatonin production and sleep quality in young volunteers. We performed two experiments in real-life home-based conditions. Young volunteers (n = 33) were exposed to four nights of one lux ALAN or two nights of five lux ALAN. Melatonin production, based on 6-sulphatoxymelatonin/creatinine concentrations in urine, and sleep quality, based on actimetry, were evaluated. Exposure to ALAN one lux during the entire night did not suppress aMT6s/creatinine concentrations but did aggravate sleep quality by increasing sleep fragmentation and one-minute immobility. ALAN up to five lux reduced melatonin biosynthesis significantly and interfered with sleep quality, as evidenced by an increased percentage of one-minute immobility and a tendency of increased fragmentation index. Our results show that people are more sensitive to low illuminance during the entire night, as previously expected. ALAN can interfere with melatonin production and sleep quality in young, healthy individuals, and both processes have different sensitivities to light.
The interest in the research of non-visual effects on human health has risen during last decade rapidly. Daylight that has humans during our evolution adapted to is considered as healthy in its natural form. In reality, the daylight inside the buildings can be different in many parameters from the exterior one. Not only intensities and spatial distribution is altered, but also spectral composition can differ significantly. Daylight transmitted through transparent elements in buildings envelope and its shading devices is filtered and therefore can have different photobiological quality compared to the daylight in exterior. Effects of the altered light conditions can have negative impact on health mostly by people that spend time continually or permanently in those internal spaces, such as long term hospitalized patients in medical facilities. The aim of the research was to find out, whether the dramatic change in the transmittance of daylights blue component will evoke the change in melatonins secretion in patients urine samples. Despite great level of circadian disruption of observed subjects a typical changes in melatonin secretion were observed as a result of altered spectral transmittances due to different glazing systems.
Light, especially its blue component, is the main synchronizer of circadian rhythms. We investigated effects of suppressed blue band of the spectrum on melatonin production and sleep efficiency in 18 young volunteers. During control days, participants lived in their home environment, and next five days in a room lit only by daylight with windows equipped with a filter blocking the blue band of the light spectrum. Light intensity, circadian stimulus and light irradiance were monitored. No significant changes in the daily pattern and total urinary 6-sulphatoxymelatonin excretion were found between control and experimental conditions. Parameters of sleep efficiency measured by wrist actigraphy were not worsened, but neutral chronotypes exhibited shortened sleep duration under light-modified conditions. We conclude that young healthy people can compensate for negative effects of transitory-worsened lighting conditions on their daily rhythms, but chronotypes and other personal characteristics may modify biological responses and should be considered.