Proceedings of: Workshop on Improving Building Design for Persons with Low Vision

Introduction

I will [restate] a little bit on what I started to talk about yesterday and talk a little bit more about buildings rather than just residences.

The Circadian System (slide 2)

We talked about the circadian system yesterday. All the rhythms in our body [run on] approximately 24 hour light-dark cycles. We have a circadian system that runs with timing slightly greater than 24 hours. We need morning light so that every day is synchronized. And we set our internal clock so that it runs with 24 – rather than 24.2 hours on average.

New Paradigm for Light (slide 3)

Melatonin Suppression

Again, this is to achieve – what we call achieve 50-percent melatonin suppression. Melatonin is a hormone we produce at night under conditions of darkness, and it’s been associated with a series of things, including sleeping.

The only thing melatonin really does: it’s a signal. It tells your body it’s nighttime. Since you’re a diurnal species, you’re going to go to sleep at night. Mice, which is a nocturnal species, are going to be active at night with high melatonin levels. And so, really, melatonin is a timing signal, okay? And, if you get enough light in the middle of the night, you’re going to cease melatonin production, suppress melatonin. We now know that that’s not something you want to do. You do not want to suppress melatonin at night, and you want to be able not to have any melatonin early in the morning when you first get up. You naturally don’t produce it during the day.

Research Projects

Light has been shown to impact all of these different groups of people (slide 7).

I’m just going to briefly talk about a couple of projects we did.

There were studies done in California a few years ago saying that daylight in schools impacts test scores and that daylight impacts performance. There was a publication out of the National Academy that criticized the results, basically saying that it was a ménage of studies and that obviously when you collect a large amount of data you are bound to get some statistical significance. So there was some controversy about it.

The approach we took was: Well, if light really impacts performance in kids or in offices, it may be through its impact on maintaining that synchrony with the solar day. It may be that in the wintertime you go to work in the dark, you come back in the dark, and you may not get, in your cubicle, enough light to synchronize your circadian system.

Daylight in Schools

So, in a middle school in North Carolina (slide 8), which has beautiful daylighting design, we collected dim-light melatonin onset data from students, which is really the timing which the melatonin starts rising in the evening. That is associated with your bedtime. You would typically go to bed about a couple of hours after your, what we call DLMO, or dim-light melatonin onset. So the later your melatonin starts rising, the later the bedtime.

Kids have a fixed time to wake up to get the school bus. So we measured their dim-light melatonin onset prior to the intervention, and then we gave them those really goofy orange glasses (slide 9). They used [the glasses] for a week in school. It was really cool to see them wearing these things.

But what these glasses do – if you look at the upper graph [in slide 9] - is basically cut your blue light. So you can see that you don’t have the circadian stimulation. So it’s like being in biological darkness, for the circadian system.

And what we saw, which is the graph in the bottom [of slide 9], is a delay in the dim-light melatonin onset from Monday to Friday by about a half-hour. So, only with five days of the intervention, not getting the morning light through the school, it delayed their bedtimes and it delayed the amount of time they slept.

So if you consider that throughout the whole winter, it may be chronic sleep deprivation that the kids might be exposed to. And it may explain why they may not perform better -- especially in the first part of the morning, which is what typically they have trouble with.

Windows in Office Spaces

The other study, conducted in 2002, was a little bit disappointing. We looked at spaces that had windows and non-windows. It was a matched population of a group of software designers that all had the same tasks. They were two-people offices. Half of the offices had daylight; the other half didn’t.

And we looked at the amount of time they were spending doing computer work, paperwork, talking, and so on [slide 10]. And what we saw was, in terms of occupancy, whether [the space] had a window or not didn’t make any difference in the wintertime. It was the amount of time you were in your office. Nobody was in their office more than half of the time.

But we did see an increase in times that people spent on the computer. That was a significant increase, suggesting that yes, in the wintertime, if they had a window in their offices, they did have an increase in productivity.

However, as with every research we do, you always have to be cautioned about your results. If we are not able to replicate our results. We went back to this place, and we were not able to replicate those results. It could be that when we went back there was a lot of changes in the organization; it was a much smaller group. For whatever reason, we never replicated those studies.

So, can I tell you that daylighting may impact productivity in offices? To me it’s still up in the air, and I don’t think I have enough data to support a statement like that.

Summary (slide 11)

I think more research is needed in terms of how daylighting may impact performance productivity in the workplace. And, if it does, it may be through maintaining synchronization with the circadian system.

So, even though we’re not ready for giving recommendations in terms of the non-visual effect of light, we have to remember that whatever recommendations we give may impact the other side of light [i.e., the circadian system].

Those with low vision may actually suffer from circadian disruption more than those without vision problems.

Daylighting does deliver the right amount of spectral timing and duration of light to positively impact the circadian system.

Daylighting in a space needs to be quantified. Just having a small window doesn’t mean you have [effective] daylighting in a space. Or having too much daylight where you have to control it because it’s glaring and uncomfortable also doesn’t mean you have [effective] daylighting in a space. So, it is important to define [effective] daylighting in a space, before we can make any statement on that.

Discussion

Performance and Productivity

Comment by Tom Williams: It’s interesting to me that there doesn’t seem to be any more research out there on the connection of daylight to productivity. That’s almost amazing, that scientifically there isn’t any kind of support for that.

Response by Mariana Figueiro: Measuring productivity is really hard.

Comment by Jeanne Halloin: The Heschong-Mahone Group out of California has other daylighting research on productivity, both in schools, and then they also did one in Wal-Mart where in the daylit areas, no matter what was being sold there, they sold like 50 percent more in the stores. So I think there are two other studies that -- if we want to start talking about daylight -- that we could look at.

Response by Mariana Figueiro: Actually, that study was the one with the schools that the National Academy questioned. So there’s still some debate about the Heschong study. Some people agree with it; other people still have some questions about the data, how the variance explains the data and so on. In [the Heschong study] with performance in offices, they weren’t able to replicate with daylight. Measuring productivity is really hard, especially measuring productivity in the field.