By Andréa de Paiva
Who have never suffered with insomnia after a few hours on the computer? How is your home lighting design during night time? What are the changes that happen in the brain when we spend more hours exposed to the light? In today's article we will discuss the insights of NeuroArchitecture about excessive exposition to light and it's impacts in the brain.
Natural light is essential to the organism's physiological temporal organisation. It allows the synchronisation of the circadian rhythm with the periods of day and night of the environment. The circadian rhythm is known as our biological clock. It covers the 24 hour period in which the activities of the biological cycle of all living beings happen. It also regulates physiological and psychological rhythms, impacting directly on wakefulness and sleep, hormones secretion, celular function and genetic expression. Therefore, it is through light that our brains synchronise a great part of its operation with the external world.
In most countries of higher latitudes such as in Russia, the time of duration of day and night varies much more through the year than in countries that are closer to de equator line like Brasil. The Russian summer has longer days when compared to more equatorial countries. Some cities that are located more to the north of Russia, like Saint Petersburg, have the famous white nights: time of the year when the sky is never completely dark during the night. At such period, the day's clarity lasts for more than 18 hours. There are also places even more to the north that the sun never sets during summer. Some examples are regions in Finland and Greenland, where the psychological impacts of the prolonged exposition to light are so strong that the number of suicides raise dramatically during summer .
Are the people who live in such countries of higher latitude the only ones affected by the prolonged exposition to light? The answer is: no. Artificial lighting can also impact the brain and life quality. And this occurs in different environments: on the streets, with lampposts and car's headlights, and inside home, with lamps and electronic devices. With the emergence of electrical illumination the man became capable of artificially extending the duration of the day. However, the brain had not enough evolutive time to adapt to this condition . For instance, the intensity of nocturnal illumination on the streets of urban centres varies between 100 and 300 lux , which is very elevated. This is why many cities are changing their public lighting in an attempt to reduce its intensity . Inside home, the screen of a computer or tablet, depending on its size, can emit around 40 lux . This excess of illumination for prolonged hours affects our physical and mental health.
In spite of our visual capacity, there are photoreceptors on the retina that work even when we keep our eyes shut (this is why it is more difficult to sleep in a bright room). And cold lights have higher impacts on the circadian rhythm than warm lights. Among the effects of the deregulation of the circadian cycle, one of the most known is insomnia. The exposition to light at night time, even in low intensity, inhibits the secretion of melatonin, the hormone that helps to regulate wakefulness and sleep. However, the problems do not end here.
The circadian rhythm pervades most brain systems responsible for mood control, like the limbic system and the hypothalamic-pituitary axis. The circadian system also regulates the secretion of glucocorticoids (among them, the cortisol). These jave important holes on the immune system and on stress control. Besides, the deregulation of the circadian cycle for a long time can also generate structural changes on the brain. Adult rats that are kept in spaces with continuous illumination presented reduction of plasticity on the hippocampus, decreasing its capacity to memorize and learn .
How can architects create more human spaces that respect our biological rhythm? The design of buildings and cities must incorporate the insights from NeuroArchitecture, specially in cases of spaces of prolonged permanence. It is necessary for the brain to recognise the passage of time through the day so it can regulate our circadian cycle. This is why windows are so important. They allow people inside buildings to notice changes on the sky according to the time. On the other hand, to artificial lighting design, it is important to know that although cold lights can offer adequate illumination not to force our eyes and to keep attention levels, they can also fool our brain and alter our circadian system when depending on how it is used .
In conclusion, it is clear that light has a fundamental hole on our health. It is the bridge that links the exterior world to our brain, helping our circadian cycle to regulate according to the environment we are in. The invention of the electric lamp allowed us to extend the day, but our brain is not hard-wired to that. Therefore, such extension, in long-term, can cause brain damage, impacting on our physical and mental health. However, not everyone know this and they might be being affected without noticing. This is why it is so important that architects and neuroarchitects pay attention to such issue. in creating more human spaces that respect our biological rhythm, we are collaborating to keep people happier and healthier.
The relation light-brain is wide and the subject is not completely discussed in this article. Soon we will discuss other aspects of such important relatio
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 BJöRKSTÉN, K., KRIPKE, D., BJERREGAARD, P. (2009) Accentuation of suicides but not homicides with rising latitudes of Greenland in the sunny months. BMC Psychiatry, 2009; 9 (1): 20 DOI: 10.1186/1471-244X-9-20