Lighting and Health

Can sleeping in total darkness help reduce cancer risks? Does insufficient exposure to daylight affect immune systems? These important topics are explored with 4 key experts.

Listen | Transcript | About NRC's Indoor Environment Program

Guests

• Dr. Jennifer Veitch
  NRC Institute for Research in Construction
• Dr. Steven Lockley
  Harvard University
• Dr. Marie Dumont
  Université de Montréal
• Dr. Anthony Levitt
  University of Toronto

Transcript - Lighting and Health

Following is a transcript of interviews conducted with Dr. Steven Lockley (Harvard University), Dr. Anthony Levitt (University of Toronto), Dr. Jennifer Veitch (NRC Institute for Research in Construction) and Dr. Marie Dumont (University of Montreal) by Sarah Dea during the summer of 2007.

Hello. This is a science podcast by the National Research Council Canada. Thanks for joining us. I'm your host, Sarah Dea. Today's show will illuminate the healing powers of light. Recent findings have sparked a lot of interest from how architects design their buildings to medical research for treating diseases like Alzheimer's.

Researchers around the world have found a key piece in the lighting puzzle. The new discovery of an optic nerve that responds to light and dark, but not through vision, has proven that light does more than help us see. Dr. Steven Lockley is a circadian effects specialist from Harvard University in Boston. He says there's a lot more to uncover in the field of lighting and health.

Lockley: Well it's a very surprising discovery. People have been studying the eyes for hundreds of years and thought that they knew everything about the eye. In the past 5 to 10 years, we've discovered a whole new photo-receptor system, a whole new way of detecting light in the eye which isn't in the parts of the eye which we were traditionally used to seeing. So we have to start to rethink all of our concepts about how light affects the brain, about how our eyes see light, what our eyes are designed to do. Because this whole new approach to a photoreceptor system isn't related to vision and is there entirely to tell us what time of day it is essentially in the outside world.

Light comes into our lives in many different ways. Dr. Anthony Levitt specializes in the study of seasonal affective disorder and therapeutic effects at University of Toronto. He says that light has a tremendous effect on how our bodies function.

Levitt: What happens is light enters the eye, into the retina, and then it goes through a series of pathways to an area called the supra-chiasmic nucleus, or SCN for short. And this SCN is basically the internal clock of the body. And it's what dictates all sorts of rhythms of waking and sleeping, a variety of hormonal rhythms, a variety of blood pressure and pulse rate and all types of other physiological rhythms. So light, through the retinas, has a direct connection to this supra-chiasmic nucleus.

Other effects on the body like on the skin, it's responsible for producing vitamin d which is essential for health. And light has other effects which are not so positive which can damage the eye, damage the skin, etc. but from a perspective of sleep and awake, what happens is in the evening when the light is diminishing and the super chiasmic nucleus is not receiving the message from the light, a hormone called melatonin peaks, rises quickly, we sleep while its at its height and in the morning when we wake and open our eyes, it immediately suppresses the melatonin and the melatonin falls into almost immeasurable levels. And this cycle of melatonin which is dictated by light is very important in a variety of mammals for controlling activities, controlling hibernation etc.

These findings have created a ripple in the science world. Dr. Jennifer Veitch is a Senior Research Officer at the NRC Institute for Research in Construction. She says that European countries recognize the importance of light and it even reflects in their building codes.

Veitch: In many, if not all European countries, the building code requires that all workplaces provide employees with access to a window, within a certain distance, usually about 5 meters. One of the consequences of that is that their buildings tend to be long and narrow, rather than square, so that people can all get access to a window or to daylight.

North American buildings, however, are still square and deep, thereby limiting window space. Perhaps building trends will shift to this construction model in order to light up our office lives.

In fact, lighting plays a key role in our functionality at work. Veitch says productivity and general happiness can be improved by working in office spaces with windows nearby.

Veitch: It certainly more likely to please more people. One thing that's been very consistent in the work done in office environments is that most people want access to a window and they grumble if they don't get it. So any design that makes it possible for more people to have that access is certainly going to satisfy them.

But for those who get minimal sun exposure, Veitch offers the following tips:

Veitch: It would be wise for people to get some exposure to bright light during the day time. It's also important to get a period of true darkness at night. People can do that by making sure they exclude light as much as possible from their bedrooms, try and make sure that street lights or neighbors lights don't shine into the room, use dark shades, they may even want to consider using a sleeping mask , so they're really in darkness when they sleep. Some experts are also recommending that for the couple of hours right before bedtime, people try to avoid working on a computer or watching tv. Because these are very bright light sources that may have a lot of the short wavelength or blue length that may interfere with melatonin, or the hormone that regulates sleep.

But what does light mean for night shift workers who sleep during the day and stay up at night working? Veitch says light exposure is still important.

Veitch: What researchers have found is that being exposed to quite bright light during the night shift, not continuously during the night shift, but short periods of time that are appropriately scheduled in relation to the start and end of the shift can help night shift workers stay alert, and being able to focus on the job is clearly important. And it also helps them to regulate their own sleep and wake cycle, so their own physical health is better when they have to work a night shift.

Veitch: Lighting and health is a very new area of research and I think that it would be premature to say that we know enough to change lighting practice based on current level of knowledge. We at NRC are active in the international commission of illumination, which provides writings on international standards on lighting. As knowledge grows, we'll be involved in writing those documents, now the main goal is do to research, which is what we need to do.

Research that can begin to tackle questions about light exposure and health. Recent headlines have suggested that working night shifts can put some people at risk for developing breast cancer. Dr. Marie Dumont is a specialist in circadian effects from the University of Montreal. She says the potential link to light and breast cancer is due to the disruption of the natural lighting cycle.

Dumont: (It has been found that exposure to light at night increases breast cancer risk and others because of the disruption of melatonin rhythm.)

La principale raison est que notre horloge biologique contrôle la sécrétion de plusieurs hormones, y compris la sécrétion de l'hormone mélatonine. La mélatonine est une hormone qui normalement est sécrétée durant la nuit et qui est très sensible à l'exposition de la lumière. Donc lorsqu'on est exposé à la lumière durant la nuit, on va diminuer, on peut même supprimer complètement la sécrétion de la mélatonine. Or, la mélatonine est considérée et connue pour être une hormone anti-oxydante, donc qui a des effets protecteurs contre le cancer. Alors de façon indirecte, on croit que l'exposition à la lumière durant la nuit, qui supprime la sécrétion de mélatonine pourrait augmenter les risques de cancer du sein. Par contre les hypothèques qu'on a présentement sont toutes indirectes. Il n'y a pas eu encore de démonstration comme quoi c'est effectivement ce qui se passe présentement chez les travailleurs de nuit, mais on sait que c'est une possibilité.

(The main reason is that our internal clock controls secretion of several hormones, including melatonin. Melatonin is usually produced at night and is very light sensitive. When you're exposed to light during the night, there will be less melatonin or none at all. Since melatonin is known for being an antioxidant, it has a protective effect on cancer. Indirectly we believe that being exposed to light at night halts melatonin production which could increase the risk of developing breast cancer. Actual hypotheses all tend toward some indirect action. We have not shown yet that this is really what happens when people work at night. But it is a possibility.)

But the solution isn't as easy as taking melatonin supplements to counteract the imbalance. Lockley says it's too soon to say.

Lockley: We don't know. Nobody's tested that. In the United States, it's a food supplement; it is much less regulated than in other countries. And therefore, we don't know the quality of the melatonin that can be bought over the counter. And after melatonin is combined with other substances like vitamins, we don't know how they interact with melatonin we also don't know how melatonin reacts with many other drugs so, an uncontrolled use of melatonin isn't something that we'd usually advised.

But light can also offer a spectrum of possibilities when it comes to diseases such as Alzheimers, which often involves disruptive sleep. Lockley says more light exposure in the daytime may help the affected sleep more soundly at night.

Ultimately, light exposure affects us all. So again, stay healthy and keep a regular schedule. Also try sleeping in complete darkness to help keep your body in rhythm.

Listeners can find out more information on the topics discussed on today's show on our website at http://www.nrc.gc.ca. Search for "lighting" and you will be led to info about lighting and health as well as office-environment research at the NRC.

Thanks for joining us!

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About NRC's Indoor Environment Program

NRC is developing a research program to identify the necessary daily light dose for good health. They plan to study specific times of day for exposure to light, particular types of lighting (spectrum), and the optimal lengths of time for exposure. The next step would be to determine how best to deliver that light dose in an energy-efficient way. Team members specialize in psychology, building physics, engineering and architecture.

NRC's Indoor Environment Program carries out applied and contract research on issues of strategic importance to the Canadian construction sector.
Find out more about NRC's Healthy Building Initiative and NRC's Indoor Environment program.