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Two Penn State professors aim to illuminate the link between light exposure and sleep patterns

AP Sunrise Maine
Robert F. Bukaty/
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AP
In this Aug. 17, 2015, file photo, a lobsterman motors through a channel between islands as he leaves Cape Porpoise Harbor at sunrise in Kennebunkport, Maine. The U.S. Senate passed the Sunshine Protection Act to switch the country permanently to daylight saving time. But, the idea has skeptics.

In March, the U.S. Senate unanimously passed a bill to make daylight saving time permanent, starting in 2023. The “Sunshine Protection Act” would still need approval in the U.S. House, and it has its skeptics. WPSU’s Anne Danahy spoke with Greg Huff, an associate professor of electrical engineering, and Rick Mistrick, an associate professor of architectural engineering. The Penn State professors developed a sensor to track light exposure and its impact on sleep.

Here is their conversation.

Anne Danahy 
Rick Mistrick. When you say circadian light exposure, what are we talking about?

Rick Mistrick
So there's a photoreceptor in the eye, that's different than the ones we use for vision, that picks up the signal that's really kind of telling us night versus day, and regulating our body rhythms from a sleep standpoint, primarily.

Anne Danahy 
And so you developed a sensor that someone could actually wear to track how much light they're exposed to on a given day. Greg, what does that sensor look like? How would it work?

Greg Huff 
So the initial sensor concept was sort of a person portable miniaturize sensor that might be able to fit on your lapel or on an eyeglass, the closer it is to your eye, the better of course, that would be very unobtrusive and have a lot of capability in detecting light.

Anne Danahy 
And what's the idea behind it? Why did you want to do this study?

Rick Mistrick 
This is Rick. What we were trying to do was develop a device that we could use to track people's light exposure during the course of a day, there are all kinds of issues related to people who get too much light late in the evening, which is going to harm sleep by suppressing melatonin in the body. You might read about that — people viewing smartphones late in the evening, but what we wanted to do is study the whole dynamic of what happens on a 24-hour cycle and how that impacts people's circadian rhythm. Really, what you want is blue light exposure in the morning, and you want to eliminate blue light exposure in the evening so that your body starts to get into that sleep mode. So this sensor would be primarily for research purposes that we can track how people in a research study were being exposed to light, and we could modify their work condition and things like that. But we'd also need to track them when they're outside in the sunlight. What we're trying to do is develop real world solutions that work in their living spaces or offices so that we can see what they're exposed to and see if we can do anything to make things better for them from a lighting standpoint, whether it's electric lighting, or providing them with more daylight at the right times of the day.

Anne Danahy 
And then how would you know about kind of the other side of that, the health impact what kind of effect this is having on them?

Rick Mistrick 
We would primarily be looking at how well they sleep. If you sleep better, chances are your health is going to be better. There are devices that pick up the daylight intervals, but some of them are on watches. And your watch isn't really determining how much light is getting to your eye. So this was really a research device that you could put on an eyeglass or you know wear around your neck that would be oriented more or less than the direction that your eye is, that we can actually track how much light is getting into the eye where those photoreceptors are that pick up the light and control the circadian rhythm.

Anne Danahy 
So I understand that the pandemic has actually kind of thrown a wrench into the research project, you haven't been able to get the sensors needed. Is that right?

Greg Huff 
Yeah, this is Greg. The pandemic created a lot of interesting challenges for this. This project really took off, I think about two months before we knew there was a pandemic. And so that was just enough time for us to you know, find the right sensors. And when we talked about the sensors for this, I think one of the things that's really key to note here is that the specific frequency of why the record identified as a frequency of interest was something that most light sensors do a reasonable to just OK job doing. It's not just like a switch that turns on and off when it sees light, we're interested in very specific frequency of light. And so these sensors actually have filters inside of them that separate out like a prism does into your reds, blues, and greens. And what we're looking for was a very specific wavelength of light is it has a known response to the human body. After identifying the sensors that were available to do this, we were able to find some breakout sensors, which are things that are put on a larger circuit board so that we can study them in the lab for ourselves. So we can characterize light sources to do that, we found some sensors and kind of had some good data coming out of this. And then we basically got shut down, they stopped selling the sensor. And since that time, there's been a real change in the market for these. The project that we originally worked on sort of had ended but the sensors have kind of reemerged in a new form now. And so you know, there's a lot of opportunity for, you know, really kind of getting back after something like this.

Anne Danahy 
What got you both interested in doing this? Was it any way related ton— there's lots of discussion about getting rid of daylight savings time, Rick, maybe we'll start with you.

Rick Mistrick 
It's definitely a health issue. And I think the Daylight Savings Time was also a health issue that people were probably looking at. And from the electric lighting standpoint, we now have LEDs and LEDs are more tunable than any other light source that we've had before. So we could potentially have a light source in the room that can deliver blue light in the morning and warmer non blue light in the evening, still making it look white but having less impact on your circadian rhythm. And that same sort of thing applies to the daylight savings time issue. The big question with Daylight Savings Time is the Senate has passed this bill that says let's go to Daylight Savings Time all year round with the medical community saying the exact opposite. Let's go to Standard Time all year round, because that better coincides with how the body wants to function. With regard to sunrise and sunset, we don't want late sunsets, because that's going to affect our nighttime sleep. And in the wintertime, we don't want to get up in the darkness, because that's going to be essentially before our body wants to wake up. And these sorts of things impact multiple diseases, cancers and that sort of thing. If your body's out of sync with its circadian rhythm in terms of how you're operating your day, that even works from the eastern part of a timezone to the western part of the timezone. There are studies that have shown that people in the western part of the timezone where the sun rises later have more health impacts of certain types than people in the eastern part, they're more in sync with their circadian rhythm, and tend to be a little bit healthier.

Anne Danahy 
But that might not be the case if they did move permanently to Daylight Savings Time, which has a lot of appeal for people, because you get a couple of hours a day light. Greg, what are your thoughts on that? What got you interested in looking at this,

Greg Huff 
I don't think anybody had the Sunlight Protection Act on their 2022 Bingo card. This is a general wireless sensor network problem. And we love these types of problems because it gets us closer to connecting with the sort of social sciences, health, human services type of environment where we can get a closer view of our impact. We're not designing a widget for a cell phone or a you know, some other type of esoteric thing that we would do academically. This is a fun project we are we make these types of sensor networks where we're interested in collecting disparate data. So data that is from sources that aren't necessarily connected to each other, integrating all that data together, making it available to researchers who are specializing in those fields so that they can make smart decisions.

Anne Danahy 
And what do you see as the next steps?

Greg Huff 
This is Greg. Since Rick and I started this. There's been some other folks also, some of Rick's colleagues have also reached out about different types of sensors and sensing networks in the wireless sensing framework of this. It's really sensor agnostic. We're really trying to take some type of sensor, we plug into this, it's body worn, it's at a fixed location. It's on a robot, you know, we can put it on cats, but we'd like to collect this data, aggregate the data, do it in a smart way that's, you know, safe, of course, maintain things like data, privacy, all those things along the way, if we're using people's phones to collect data to make sure that we're doing that in the right way. Yeah, maybe in a year someone says this other frequency is really good for learning how to read better. OK, that's great. We can just take the same sensor and say, you've already collected all these measurements. Can we go back and look and see how this works?

Anne Danahy 
Professors Greg Huff and Rick Mistrick, thank you both for talking with us.

Rick Mistrick 

Thank you, Anne.

Anne Danahy is a reporter at WPSU. She was a reporter for nearly 12 years at the Centre Daily Times in State College, Pennsylvania, where she earned a number of awards for her coverage of issues including the impact of natural gas development on communities.