The Effects

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™. Explore the categories to learn more about the effects of light.


A disturbed circadian rhythm

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.

Call for personalized light

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. BCL creates a future for indoor lighting where the circadian rhythm is synchronized with personally adapted light recipes.

A disturbed circadian rhythm is seen as a likely link to cancer.


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-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.

Sleep deprivation and the circadian rhythm

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.

Appropriate light can protect against detrimental light at night

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.



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.

The negative effect of poor lighting is even more significant than the positive effect gained from regular physical exercise.



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.

Reduce stress

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

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

The biological effect of light is bigger than most people are aware of. 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. These are wavelength, intensity, direction, timing and duration. Our lighting environments are designed to have the same positive effects as daylight, securing a natural synchronization with biological clocks.

Want to extend your knowledge?

Learn more about scientific research and studies related to the effects of light on humans in different areas and conditions. Expand the tabs to read more.

The importance of sleep

Sleep plays a critical role in functioning. A good nights sleep prepares us for the activities during daytime. But sleep is not a passive state of rest. Sleep is also a time when part of the body is more active. When blood pressure drops and breathing becomes more regular and slower, the release of growth hormones increases. Activities such as muscle growth, cell repair, protein synthesis and digestion are often at peak during sleep.

Factors influencing sleep

  • Light. Light affect sleep directly by suppression of sleep hormone melatonin thus making us alert but also by synchronizing the internal clock affecting our time to sleep.
  • Age. A gradual decline of need for sleep from newborn into adulthood.
  • Sleep environment. Noise, temperature and light are all factors than can affect sleep.
  • Medical conditions. Pain and discomfort makes it more difficult to sleep. Medical conditions affects sleep regulation.
  • Psychological conditions. Anxiety, stress and depression makes it more difficult to sleep.
  • Medications (beta blockers, antihistamines, alpha blockers, antidepressants, sleeping medications) can disturb sleep.
  • Drugs and substances (nicotine, caffeine, alcohol) have an effect on sleep.

People in industrialized countries spend less time outside than before and are often
exposed to as little as 1 hour of daylight. Without light, synchronization of the sleep rhythm becomes compromised.

Factors which cause sleep disruption

• Too little daylight to synchronize with the solar day.

• Light outside the solar day.

• Our social rhythm is out of sync with the solar day.

• Our social rhythm varies (shift work, late night out etc).

There is growing evidence that we sleep too little. Short term effects of sleep deprivation include direct physiological effects on hunger hormones. When sleep deprived at night, the hormone ghreline that stimulates appetite, increases in our blood. Food ingestion at night is a time when the body process glucose more slowly and cells have a lower insulin sensitivity than during daytime. Furthermore, sleep restriction accentuates increased activity in regions in the brain involved in reward in response to food stimuli.

Short term effects of sleep deprivation

  • Physiological reactions. Increased blood pressure, impaired control of blood glucose, reduced insulin sensitivity, increased inflammation.
  • Sleepiness.
  • Decreased mental capacity. Lack of logical reasoning, decreased mathematical capacity, lower concentration, poor working memory, poor creativity.
  • Bad mood, increased impulsiveness and increased anger.
  • Poor judgement.

Already after 3 days of sleep extension in men who habitually sleep for short time periods, positive effects on insulin metabolism and an increase in testosterone was seen.


Long term consequences of sleep deprivation

  • Mood disorders
  • Obesity
  • Diabetes
  • Hypertension
  • Cancer

The long term consequences of sleep deprivation cause widespread health problems. Shift workers, making up 15-20 % of European and US work force are at particular risk of circadian rhythm and sleep disruption. Shift workers have an increased prevalence of cardiovascular disease and cancer and sleeping problems are common.


The numbers

15 % increased mortality risk amongst people who sleep 5 hours or less per night

20 % of all motor vehicle accidents in the US are caused by sleep deprivation

30 % of the population experience sleep related problems.

33 % of drivers have fallen asleep at the wheel

50 % of all night shift workers report regularly nodding off and falling asleep when they are at work.

7 hours - amount of sleep most people need per night

6.5 hours - average sleep time


How to improve sleep

Prepare your sleep in advance. Try to wind down and avoid too much light an hour before going to sleep. Try to have regular sleeping schedule and avoid exercise three hours before going to bed as exercise stimulates the body to secrete the stress hormone cortisol. Also avoid food several hours before sleep. Light in the evening can interfere with sleep but bright light in the morning suppress melatonin and helps synchronize the sleep-wake cycle. Try to get enough light during daytime and especially during the early hours.



The Division of Sleep Medicine at Harvard Medical School and WGBH Educational Foundation

Medic et al. Short- and long-term health consequences of sleep disruption Nature and Science of Sleep 2017:9 151–161

Figueiro and White Health consequences of shift work and implications for structural design Journal of Perinatology (2013) 33, S17–S23

Johnston et al. Circadian Rhythms, Metabolism, and Chrononutrition in Rodents and Humans REVIEW FROM ASN EB 2015 SYMPOSIUM

Relation between ADHD and a disturbed circadian rhythm

ADHD (Attention Deficit Hyperactivity Disorder) is a neurodevelopmental condition with increasing prevalence affecting around 7-8 % of children. It often continues into adulthood. Roughly two thirds of children diagnosed with ADHD use medication for their condition.

Research has shown circadian rhythm disruption in adult ADHD with delayed sleep onset, phase delay of dim light melatonin onset (DLMO) and an association with evening chronotype. A circadian phase disturbance contributes to both subjective and objective dysfunction in adult ADHD.

Insomnia amongst adults and children with ADHD is common, which is directly related to a disturbed circadian rhythm. About half of the children suffering from insomnia receiving melatonin also use ADHD medication. An increase in prescription of melatonin has been reported.

Bright sunlight is known to enhance and reinforce our own natural circadian rhythms. Emerging research on light therapy has shown beneficial effects on circadian disruption and alleviation of ADHD symptoms.

One study found

  • Improved symptoms of ADHD especially symptoms of impulsiveness, inattention, difficulty sustaining effort and fatigue
  • Improved mood symptoms
  • Advance in circadian preference

Another study found

  • Earlier DLMO
  • Earlier mid-sleep

These promising study results highlight the positive effects of a normalised circadian rhythm for persons with ADHD, where BCL and dynamic lighting can be extra beneficial.


Coogan and McGovan A systematic review of circadian function, chronotype
and chronotherapy in attention deficit hyperactivity disorder
ADHD Atten Def Hyp Disord (2017) 9:129–147

Fargason et al Correcting delayed circadian phase with bright light therapy predicts improvement in ADHD symptoms: A pilot study Journal of Psychiatric Research 91 (2017) 105-110

Rybak et al An Open Trial of Light Therapy in Adult Attention-Deficit/Hyperactivity Disorder J Clin Psychiatry 2006;67:1527–1535

Furster and Hallerbäck The use of melatonin in Swedish children and adolescents—
a register-based study according to age, gender, and medication of ADHD
Eur J Clin Pharmacol (2015) 71:877–881