It’s not enough to set your alarm clock – you also have to set your internal biological clock to truly awake and become alert. Thorbjörn Laike and his research colleagues at Lund University are studying how we can affect our wakefulness and well-being with the help of LED lighting.
A single candle or LED lamp is enough for us to be able to see. Yet we are dependent on natural light and the rhythm it creates. Why is that and how does it work?
“We are acclimatised to daylight and its variation throughout the day. Daylight provides short-wavelength blue light that affects us, especially through our eyes. We have something called the ‘third receptor’, that is, cells in our eyes that are sensitive to specifically short-wavelength blue light. The blue light affects our wakefulness and sets our internal clock through hormones by blocking the production of melatonin in the pineal gland. This in turn sends signals to the adrenal cortex, and the cortisol production increases, which in turn causes other reactions and we become more awake. At night the absence of light makes us no longer block the production of melatonin, and we become sleepy.
We know that we need light in the morning to be able to set our biological clocks correctly. Most of us have an inner circadian rhythm, which is controlled completely internally, which is slightly longer than 24 hours, and therefore we would constantly be setting our clocks ahead – if there was no light.”
What happens when we don’t get enough daylight?
“Even on a semi cloudy day, the light intensity outside is 8–9000 lux. If you step inside, approximately one to two metres away from the window, the access to light decreases to 1000–1500 lux, and continues to drop rapidly. The first studies on how light affects our wakefulness and sleep, which Rickard Küller and his colleagues initiated here in Lund, were about how school pupils are affected by the time they spend in classrooms with and without daylight. The study took place during one academic year, and demonstrated that the pupils who experienced the most daylight in class were more active and performed better on, for instance, exams in reading comprehension and math.
A general lack of daylight can affect those of us who live far away from the equator. More than half of us claim that we experience ‘normal’ winter fatigue – what we call ‘seasonal tiredness’ (a mild form of SAD, Seasonal Affective Disorder) – which can be linked to the days becoming increasingly shorter during winter. Winter fatigue may be caused by the transition to darkness in the autumn, or the impact it has throughout the entire period of darkness.”
Isn’t it enough to turn on the lights indoors?
“For a long time we have extended the period we stay awake during the winter months through lighting. Up to and including the light bulb, our sources of light have been weak with a low-intensity, long-wavelength, yellowish light. This light doesn’t affect us in the same way that daylight does. But when first fluorescent lamps, and then particularly the new LED lamps, were developed, everything changed.
LED was the technology that after a long search was developed to create energy efficient lighting where the majority of the radiation was not lost in the form of heat (as with the light bulb). The technology is based exclusively on short-wavelength and intense light, and its composition is therefore not the same as daylight. Daylight is also dynamic and always changing in ways that cannot be matched. What we hope for is to be able to produce a light that spectrally begins to resemble daylight while being energy efficient.”
LED lamps today can still have an effect on us. What does that mean?
“LED lighting can help us to produce so much short-wavelength light that it may affect our light-sensitive hormonal systems. This makes lighting into an issue of environmental psychology.
Since 2008 we have studied what is required of lighting to be of good quality to people, through our collaborative project CEEBEL. For example, we see that timing – when we are exposed to much light – is very important. The research on wakefulness in school demonstrates that it is appropriate to increase light in the morning to increase alertness in young people. The next step is to try to evaluate if it is possible to improve study results with the help of lighting.
Also when it comes to winter fatigue, SAD, experience has shown us that strong lighting in white rooms – light therapy – helps. We now know that, even in this context, short-wavelength light is the most essential aspect, but also the direction of the light is important. With ambient light that, for instance, is reflected by the walls and the ceiling, the lighting conditions more closely resemble daylight.
In anticipation of becoming better at mimicking daylight and its variations, we are working on how to use the right light at the right time – in schools, workplaces and retirement homes, etc. – but also to adjust the amount of light for each individual.”
Text: Pia Romare
Photo: Kennet Rouna
Thorbjörn Laike is a professor in Environmental Psychology at the Department of Architecture and the Built Environment at the Faculty of Engineering, as well as the director of CEEBEL.
CEEBEL (Centre for Energy Efficient Lighting) is a collaborative project funded within the Swedish Energy Agency’s programme for energy efficiency within the field of lighting. The aim of CEEBEL is to bring researchers from different higher education institutions together, and help them connect so that they can generate new research projects related both to the human being and to energy efficiency.