Lighting to wake you up?
One criticism of the current generation of energy saving lightbulbs is their colour, but it's not just that people find blue light a bit harsh, scientists are also discovering that blue light can affect your sleep cycle, especially if you're reading before you go to sleep.
Chris spoke to Russell Foster, Professor of circadian Neuroscience at Oxford University to find out how lighting might be affecting our lives.
Russell - Well, the eye of course detects light in two very different ways. The eye is used to construct an image of our world and of course, that's vision and we've understood that for centuries. But of course, there's another function of the eye and that's to detect overall levels of brightness in the environment and you use this to regulate physiology ss diverse as the body clock, levels of alertness. And what's turned out to be really remarkable is that there are different sorts of receptors - the classical receptors, the rods and the cones are building the image of the world and then there's another light sensor called a photosensitive retinal ganglion cell which is measuring brightness and firing information directly into those areas of the brain which regulate these non-visual responses to light.
Chris - So, we've evolved as humans to wake up in the morning and go to bed when it gets dark. So, what influence and what impacts are there on our health of having artificial light?
Russell - Well, when Edison invented the light bulb and it became widely used in the 20th century, it allowed us to essentially invade the night. And it's been estimated that even people who aren't doing things like shift work are probably sleeping 1 ½ to 2 hours less every night because of the use of artificial light. And overall, the levels of sleep we're getting as a society and as individuals is vanishingly small compared to a pre-industrial age. So, what artificial light has done is compress a really rather expanded sleep period into perhaps as little as 6 hours, 6 ½ hours for most people.
Chris - What about the type of light though because Edison's light bulb put out a certain range of wavelengths that were effectively a nice comfortable daylight resembling glow? We're now making light bulbs that actually, I'm just looking at some, that are powered by LEDs that produce quite a harsh blue colour. So, does the type of light potentially have an impact?
Russell - Yes, it does. These photosensitive ganglion cells are pure brightness detectors. And interestingly enough, they're most sensitive to the blue wavelengths of light. So, these blue enriched LEDs will very much stimulate those cells that we use to regulate our body clocks, our levels of alertness, and indeed, our pupil size.
Chris - And of course, one of the places where we're seeing a lot of these LEDs being used is in computer screens which if you believe what Facebook and Twitter tell us, the last thing, something like half of young people in Britain and the probably the rest of the world do before they go to bed is to check what's on their Facebook page or their Twitter account. So, we must be getting quite high exposure to this very blue-dominated light late at night.
Russell - Yes, it's absolutely fascinating because of course, there is this biological predisposition for teenagers to go to bed late and get up late. But it's enormously exaggerated by the sorts of things you're talking about. Checking one's Facebook and going on and exposing one's self to these screens. Now, it's not particularly bright and the earliest screens probably weren't bright enough to shift the body clock which needs quite a bit of light. But they certainly would've been bright enough to raise levels of alertness and therefore, delay night time sleep. So, these screens are sort of exaggerating this biological predisposition for teenagers to go to bed late and get up late.
Chris - What about in the workplace or just in the home, more generally, as we adopt bluer dominated lighting? Is that always a bad thing? Is it not good in the morning to have that because it might make me feel a bit perkier?
Russell - I think that's exactly the right thing and it's the intelligent use of these light sources that could be incredibly powerful. So, what you need is bright morning light exposure to set the body clock to local time and that will be terrific. So, exposure in the morning to these bright light sources will be very good and in addition, they will increase levels of alertness in the workplace. The downside would be having bright light exposure at the other end of the day when you're trying to get to sleep and one of the most extraordinary things is, I've seen some of these devices being incorporated into bathroom mirrors. Now, the last thing many of us do of course is clean our teeth in front of a bright mirror before we go to bed and of course, that hugely increases our levels of alertness and delays our sleep. So, it's not just in sort of computer screen type devices, but it's in many applications where inappropriate light exposure is not necessarily going to be good for us.
Chris - Do you think then that now, we can make things like LEDs that can put out different wavelengths, we could have timed LEDs that will be very blue dominated in the morning to get us going. Then as the day goes on, they can be tuned so that people do feel more relaxed as the day goes on. And then as you go to bed at night, you're seeing much more red dominated light and this doesn't have this enlivening effect when you're trying to go to sleep.
Russell - I think that's a very exciting application. I mean, the intelligent use of these devices could be incredibly powerful in fine-tuning both our visual biology, but also, the biology of the sleep-wake cycle.
Chris - Is there actually any evidence that it is having ill-effects though because everything you said so far, I don't disagree with, but it's all based on - well, this is going to make people feel more awake or it's going to put us out of step with what our body clock should be doing, but is there any evidence that's actually bad?
Russell - We have a few studies that have emerged which have looked at the impact of iPads and devices like that on supressing melatonin. And of course, melatonin suppression is often used as a surrogate measure for the impact of light on the body clock. And these devices were shown to supress melatonin and so, yes, we do have some real biology that the non-image forming photoreceptor systems, the non-visual systems are being affected by these devices.