Effects of light

The biological effect of light is bigger than most people are aware of.

Light affects all species on earth, especially humans. Evolution has made natural variation of light essential for mankind, a need that hasn’t changed despite our changed behaviors. Whilst humans have existed on earth for more than 10,000 generations, only the last 5-6 of these generations have spent their time primarily indoors. 

Light affects us in mainly three ways; visually, emotionally and biologically.

The visual dimension of light is the traditional one, affecting what we see and how we are seen. The emotional dimension has to do with how light affects our mood, energy and state of mind. Interest in the third dimension, focusing on how we are biologically affected by light, is rapidly increasing. This is due to more and more people realizing the potential in using light to enhance alertness, cognitive performance and the sleep/wake cycle. BioCentric Lighting™ is a game changer in effectively handling all three of these dimensions of light.

Light has a significant effect on biological functions and our daily routines, and is central to our well-being. Exposure to daylight affects our sleep quality, efficiency, alertness and similar other important factors for our health. Research has led to a number of exciting study results that form the basis of BioCentric Lighting™.

Light affects normal human physiology in a profound way such as sleep and growth. With light we can affect mood, improve sleep and treat depression. But light also has a direct alerting effect and can affect productivity, learning and memory consolidation.

Other effects of light on humans are diseases that demonstrate seasonal and diurnal patterns. Seasonal affective disorder (SAD) and acute myocardial infarction (AMI) are two examples, occurring in a higher frequency during the darker months of the year¹. Also several of the basic human behaviors and bodily physiology show a diurnal, in some cases even a seasonal, rhythm and are affected by light for their expression.

With more and more time being spent indoors and in front of screens, our bodies fail to synchronize with sunlight. To maintain and improve our well-being and create a better future for our children, it is vital that we maintain our circadian rhythm. With BioCentric Lighting™ we control and combine the light parameters that influence your physiology. 

Health

Humans are created for a circadian rhythm with day and night. Nowadays people reside indoors most of their time and do not receive natural synchronization with exposure to sunlight. Light indoors usually does not have the same intensity as daylight and in addition, there is not the variation in color spectra which is present in daylight. Exposure to light is also common at night, a time when sensitivity to light exposure is greatest, which further augments the desynchronization with daylight¹³. Social life patterns are often also separated from the solar day, which furthers a phase shift between circadian rhythm and rhythm of life. Shift workers often have a circadian misalignment and are at increased risk of developing cardiovascular disease, impaired glucose metabolism, and cancer¹⁴.
Modern lifestyles vary significantly in relation to the natural light-dark cycle. Eating habits, exercise, traveling and work commitments affect our access to daylight. These influencing parameters are individual and affect our sleep-wake cycle. Sudden external disturbances of the rhythm such as moving rapidly across latitudes cause changes in the rhythm. Clocks in different tissues adapt to these changes at a different rate causing de-synchronization. Light can be one disturber to the rhythm – feeding, exercise and outside temperature are others³⁸.
Sleep
Sleep-related problems are very common in society today. Lack of sleep leads to poor judgment, increased impulsiveness and lack of memory. Sleep patterns are directly connected with our circadian rhythm. A summary of research shows that light can correct a disturbed circadian rhythm²⁰, ²¹. Light exposure in the evening/early night shifts the melatonin onset to a later hour the next night, and light in early morning pushes the melatonin onset to an earlier hour the following night¹³. The strength of the synchronization depends on the light distribution and on the time of exposure²². An improved circadian rhythm is associated with improved sleep and reduced depressive symptoms²³.
Depending on diagnostic criteria, studies report 10-30 % of the general population suffering from some form of sleep-related disorder. Often there is a phase shift where the rhythm of life, the circadian rhythm, and the hormones associated with metabolic rhythm do not harmonize¹⁸. A disturbed circadian rhythm has been shown to increase the risk of cardiovascular disease, diabetes and is seen as a likely link to cancer¹⁹.
Reducing exposure to blue light by wearing protective glasses in the evening is one way of improving night sleep²⁹. On the other hand, light, and especially blue light, in the morning stabilizes the circadian rhythm¹³. It also appears to be protective against light at other times which otherwise could shift the circadian rhythm and disturb sleep³⁰, ³¹, ³².
Light as a treatment for depression
Light has been used to treat depression for many years²⁴,²⁵. Published studies also show that a combination of pharmacological therapy and light is more effective than psychopharma alone, and chronobiological therapy is advancing²⁶. Similarly, daylight exposure has been used to reduce depression symptoms in individuals with dementia, a group that is largely affected by depression²⁷. Seasonal depression seems to be equally effective treated with blue-enriched white light at 750 lux as a standard bright lux at 10 000 lux²⁸.
Light exposure for the eye
Myopia is characterized by a growth of the eye where the eye is becoming too long in relation to the optics of the eye, placing the image in front of the retina. In a recently published report, light intensity and spectra were shown to affect the growth of the eye in an animal model³³. In another recent report, it was found that time spent outdoors prevents the development of myopia³⁴. In yet another study, it was also shown that time and intensity of light is crucial for the development of myopia³⁵. Receiving less than 40 min of bright daily light (> 1,000 lux) could predispose to faster growth, and it was speculated whether there is a minimum amount of light required to reduce growth.

Function

Alertness
Light affects our alertness⁶. Exposure to blue-enriched white light has an awakening effect³ and monochromatic blue light (420 nm) induce greater alertness compared to light with longer wavelengths, which is apparent also after long time exposure⁷. It is speculated whether this effect at daytime might be mediated via direct intrinsically photoreceptive retinal ganglion cells’ projections to the thalamic regions in the brain⁷.
Cognition, productivity, and concentration
Blue light seems to improve cognition⁸ and positively affect long time memory consolidation⁹. Also, blue light exposure among office workers has been shown to have positive long-term effects on productivity and concentration¹⁰, ¹¹.

Emotion

Mood
Lower mood is an effect of poor lighting¹. In a population-based study in Finland, self-reported inadequate indoor illumination is associated with mental ill-being². In the same study, it was found that the negative effect of poor lighting is even more significant than the positive effect gained from regular physical exercise². On the other hand, light can also enhance mood. Blue-toned white light has a direct mood enhancing effect³ and several studies indicate that dawn simulations in the morning improve the subjective perception of well-being⁴.
Stress reducing
The importance of adequate lighting in schools and its effect on well-being is important to reduce children’s level of stress. A group of Swedish researchers have argued for better lighting conditions to improve school environments⁵.

Effect of light dependents

  • Intensity
  • Timing
  • Wavelength
  • Length stimuli
  • Previous light history
  • Other influences such as food and excercise

Positive effects of the right light

  • Synchronizes a disturbed circadian rhythm and promotes sleep
  • Efficient treatment of seasonal affective disorder
  • Augmented effect in treatment of depression paired with pharmacological treatment
  • Increased learning among school children
  • Increased melatonin levels among stroke patients
  • Cyclic light helps premature children with weight gain and subsequently shortens length of hospital stay
  • Light appears to be protective for myopia development

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