Host: Nick Howe
Welcome back to the Nature Podcast. This week, what a sniff reveals about consciousness…
Host: Shamini Bundell
And the relationship between vaccines and antibiotic use. I’m Shamini Bundell.
Host: Nick Howe
And I’m Nick Howe.
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Interviewer: Nick Howe
Imagine you’re walking in a park. It’s a beautiful sunny day with flowers everywhere and what a lovely smell.
[Inhales]
Ah… Now, I’m not just trying to keep you sane during lockdown. Humans often inhale through their nose when they smell something nice. It’s an automatic response. Now, researchers think that this sniff reflex could help doctors assess an immobile patient’s level of conscious. That’s according to a new study in this week’s Nature. I called up one of the authors, Anat Arzi, to find out more, and she started by telling me about different levels of consciousness – in particular, the difference between a vegetative and a minimally conscious state.
Interviewee: Anat Arzi
A person that is diagnosed in a vegetative state is someone that has a sleep-wake cycle and the eyes are spontaneously open. However, we have no evidence for any signs of conscious awareness for the self or to their environment, so we have no ability to communicate with this person and this person has no ability to communicate. For minimally conscious patients, they have a severe altered consciousness. However, there are subtle signs of consciousness. We have evidence that this person has some awareness of the environment.
Interviewer: Nick Howe
And why is it so important for clinicians to be able to determine between whether someone is in a vegetative state versus a minimally conscious state?
Interviewee: Anat Arzi
They have to make really hard decisions. They have to make decisions that could determine what kind of clinical treatment the patient is going to get. For example, if you think that the patient has no pain sensation, you wouldn’t give them painkillers. However, if you are mistaken, they are going to suffer. And in some countries, they’re also facing the decision about end of life about this diagnosis, so they actually determine whether the person is going to live or die.
Interviewer: Nick Howe
And in this latest work that’s being published in Nature this week, you and your team have been trying to find a new way to do that. Can you describe what it is that you are doing to try and distinguish between these vegetative and minimally conscious states?
Interviewee: Anat Arzi
Olfaction, the sense of smell, has a unique interaction with consciousness. At the neuroanatomical level, it has a direct path to the brain, which other senses like vision and audition don’t have this unique pathway. The other thing is that we have this amazing tool in the sense of smell and this is our sniff. And what do I mean? If I walk by my favourite bakery and they just bake a fresh croissant, I will take a deep inhale. However, if I walk by a public toilet, I will usually take a small inhale or even stop breathing for a few seconds, and this change in nasal airflow is our sniff response, and the sniff response is an implicit non-verbal tool for processing. I do not need to ask you whether you like the odour or not. I can just measure the respiration and actually, in a way, read your mind.
Interviewer: Nick Howe
And so, you were trying to identify if this sniff response could be used to determine between these vegetative and minimally conscious states. So, how did you do that?
Interviewee: Anat Arzi
So, every time we can came to the hospital and met the patients, we recorded their nasal respiration using a small nasal cannula. Then we explained to the patient that we are going to present a few odours. One of them was pleasant, one of them was unpleasant, and one just contained no odour. We presented each odour for about five seconds, and then after we assessed the consciousness level of the patients, whether the patient is responsive, then in the lab we tested whether the magnitude of the sniff response is different between the groups, and we found that indeed people who were in minimally conscious states had a significant change in their sniff volume when we presented an odour. However, when we presented an odour to people who were not responsive, we didn’t find any change in the sniff volume at the group level.
Interviewer: Nick Howe
How subtle of a difference was it? Is it something you could see happening or was it more something you had to measure in the lab?
Interviewee: Anat Arzi
So, there is variability between the patients. So, in some cases, you can see the modulation at the single trial level, and in some cases, you need to do a bit more of an analysis to see a statistically significant result. But what I was telling you is what we found at the group level. What we actually want is to know whether this could be informative at the single patient level. So, we wanted to know whether we can use the sniff response to know whether a person who is now unresponsive is going to recover consciousness, is going to transition into a minimally conscious state, and to do so, we had to define what is the sniff response. So, we had to define a threshold. And what we discovered after applying this threshold is that every single patient that was unresponsive but had a sniff response later on recovered consciousness and transitioned into a minimally conscious state, which was quite exciting. In addition, all the patients that did not recover and remain unresponsive during this study did not have a sniff response. So, if I need to summarise this in one sentence it’s that if you have a sniff response, you will most likely recover consciousness.
Interviewer: Nick Howe
How easy would something like this be to use for a doctor or clinician?
Interviewee: Anat Arzi
Quite simple, actually. All you need is a nasal cannula that is connected to a device that will record the pressure in the nose, and you just need to present the patient with an odour. Actually, you can use just one odour and see if they modulate their respiration. So, this could be used at the bedside and it’s affordable and accessible and quite easy to use.
Interviewer: Nick Howe
And dare I ask, what are the smells that you used?
Interviewee: Anat Arzi
So, the smell that we used for the pleasant odour was a shampoo-like odour, and for the unpleasant odour it was rotten fish, which is profoundly unpleasant, trust me. If you need a big change in respiration, you need to choose something that is really unpleasant.
Interviewer: Nick Howe
And for the doctors and people who would be using this, like you did, would they have to measure things in the lab or would they just be able to determine just from waving it under their nose that this person has a sniff response?
Interviewee: Anat Arzi
So, in some cases, you can detect it by eye, but now at the lab of Professor Noam Sobel at the Weizmann Institute, they are developing a simple tool that could be used using a simple application on your phone, so hopefully this will be available in the near future.
Interviewer: Nick Howe
That was Anat Arzi from the Weizmann Institute in Israel and the University of Cambridge here in the UK. To find out more, check out the show notes, where there’ll be a link to the paper.
Host: Shamini Bundell
Coming up, we’ll be learning about the role of vaccination in preventing antibiotic resistance. Before that, though, it’s time for the Research Highlights, read to you this week by Noah Baker.
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Noah Baker
Greenhouse gases will make us stupider – at least, that’s according to a new study. Scientists know that human cognition declines as carbon dioxide levels rise in the air they breathe, so a team of researchers investigated how much of an effect various emissions scenarios could have on our smarts. If greenhouse gases continue to rise unabated, atmospheric CO2 levels are forecast to hit 930 parts per million by 2100. The team used this to predict indoor CO2 levels, which are typically much higher because of people breathing out. They calculated that the air in a typical school room full of students could reach 1,400 parts per million of CO2. By extrapolating from other studies about CO2 and cognition, the researchers predict that, at that level, scores on tests of basic decision-making could be 25% lower than they are today, and for more complicated strategic thinking, 50% lower. Better building ventilation could help, but not much because outdoor CO2 levels would be so high. It seems then that cutting greenhouse gas emissions is the best way to stave off this slow-thinking future. Read that study over at Geohealth.
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Noah Baker
Scientists have worked out how a chameleon gemstone changes colour by outwitting the human eye. The rare jewel alexandrite has the remarkable ability to change colour under different lighting. Alexandrite appears to be a brilliant emerald green in daylight but a rich ruby red under candlelight. Scientists measured the amount of light that the stones were transmitting in each scenario. Chromium atoms in the gemstone absorb both yellow and blue light, leaving only green and red sunlight to reach the viewer’s eye. That helps to explain why the gems will look green in sunlight, as sunlight contains far more green than red wavelengths. Candlelight, on the other hand, contains much more red light. In most circumstances, the human visual system corrects for a light source’s colour cast i.e. it would still interpret the stone as the same colour as it is in sunlight, but alexandrite overrides that correction by completely mopping up yellow and blue light without absorbing red or green. The eye simply sees the more prominent red. Catch a glimpse of that paper over at Scientific Reports.
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Host: Shamini Bundell
Vaccination is a critical tool for public health, and this is particularly the case for lower- and middle-income countries. Here, vaccination programmes can ease the burden on healthcare systems and prevent the need for future treatments. This week in Nature, Joe Lewnard leads a study that’s been identifying how lower- and middle-income countries could cut down their antibiotic use through increased vaccination, maybe even preventing the rise of antibiotic resistance. Reporter Ali Jennings called up Joe to find out more, and started by asking him about the scale of the antibiotic resistance problem.
Interviewee: Joe Lewnard
The problem we’re dealing with is that antimicrobial resistance represents a threat to human health and wellbeing along the scale of climate change, for which few solutions are on the horizon. The goal of this study was to identify the effect of pneumococcal and rotavirus vaccines on the incidents of antibiotic-treated acute respiratory infection and diarrhoea, and to answer the question of how scaling up receipt of these vaccines in the developing world could lead to reduced antibiotic treatment for children across all lower- and middle-income countries.
Interviewer: Ali Jennings
And why is it that these countries are suffering more from antibiotic resistance?
Interviewee: Joe Lewnard
In these countries where financial circumstances are more tight and perhaps treatment capacity is limited, infection with a resistant organism can be much more threatening than it would be in, for instance, a higher-income setting where perhaps a last-resort antibiotic could be more readily available to a person who needs it. Resistant infection that fails initial first- or second-line treatment in a setting like this could mean death for a child.
Interviewer: Ali Jennings
So, how do you go about estimating the amount of antibiotics that could be saved through increased vaccine usage?
Interviewee: Joe Lewnard
First, we need to estimate the incidents of antibiotic-treated infections among children under five in all of these countries. We were able to use surveys which collect data on recent illness as well as vaccine receipt based on mothers’ report of children’s experience with acute respiratory infection or diarrhoea. We next say, what is the proportion of those illness episodes that’s caused by pneumococcus and rotavirus and therefore preventable by vaccines?
Interviewer: Ali Jennings
And were there any countries that you felt that you really would have liked to have got data from but you actually couldn’t?
Interviewee: Joe Lewnard
So, we had a problem when we were using these surveys, which is that they only cover a limited set of all lower- and middle-income countries, so what we were able to do was take sweeps of variables that are measured at the national level, addressing all aspects of health and socioeconomic wellbeing, and use these variables to calibrate a model to project what the likely incidents of acute respiratory infection and diarrhoea would be in the countries without surveys.
Interviewer: Ali Jennings
So, what did you find?
Interviewee: Joe Lewnard
What we found is that pneumococcal vaccines and rotavirus vaccines can prevent about 20% and 11% of antibiotic-treated episodes and in addition, scaling up receipt of these vaccines could prevent an additional 40 million episodes of antibiotic-treated illness.
Interviewer: Ali Jennings
How feasible is it to actually achieve this higher level of vaccination?
Interviewee: Joe Lewnard
One of the issues that really right now limits the effect of pneumococcal and rotavirus vaccines is not only limited receipt in countries where they’re recommended but even more simply just that a lot of countries still do not recommend their use, perhaps due to under-appreciation of the impact of diseases that they cause or a lack of access to reduced pricing-type arrangements that, for instance, Gavi, the Vaccine Alliance has made possible for the poorest countries of the world. There is a challenge that as countries transition to lower-middle-income status, they lose eligibility for some of these benefits and have to take on the responsibility of financing their own vaccination programmes, and so there is a need for data like this that shows the comprehensive effects of these vaccines to make sure that health ministers are aware of the benefits of these vaccines for children in these countries.
Interviewer: Ali Jennings
Is there any way of getting an idea of how using that much less antibiotics would affect the amount of antibiotic resistance in the bacterial population?
Interviewee: Joe Lewnard
This is a really hard question to answer and not one that we had bandwidth to get into in this study. However, knowing that antibiotic use is the most proximate factor determining the selection of resistant lineages for human pathogens, prevention of antibiotic use is probably our first target for reducing resistance.
Interviewer: Ali Jennings
And have things been disrupted by the ongoing COVID-19 pandemic?
Interviewee: Joe Lewnard
I think every infectious disease epidemiologist can tell you that they’ve been disrupted by the COVID-19 pandemic. We have now the first data emerging from the United States showing 50-70% reductions in receipt of measles and HPV and other vaccines in this country, and we can probably only imagine the disruption that this will cause in the developing world where many of our gains in vaccine delivery are now at risk. We know that the polio eradication programme has had to halt, which is troubling and stains to erode years and years of hard work and progress, so there’s, I think, a lot of questions that will also come around these other conditions that are vaccine-preventable in the context of COVID-19.
Host: Shamini Bundell
That was Joe Lewnard from the University of California, Berkeley in the US. You can find a link to that new study in the show notes.
Host: Nick Howe
Finally on the show, you may have heard of the Nature Briefing, Nature’s daily or weekly pick of science news and stories delivered directly to your inbox. Well, Shamini and I have been scouring it to bring you some non-corona science news. Shamini, what have you found this week?
Host: Shamini Bundell
Well, the Briefing this week sent me to Chemistry World, where I’ve been learning about someone called Eunice Foote.
Host: Nick Howe
I have never heard of them. Tell me more about Eunice.
Host: Shamini Bundell
Well, people having not heard of her is sort of the point of the story. So, she was an amateur scientist and inventor and various things in America in the 1800s, and she published this paper in 1856 which was basically the first time that anyone had linked carbon dioxide in the atmosphere to warming, global warming, essentially, although that wasn’t the context that they were thinking about it back then.
Host: Nick Howe
Oh wow, so all the way back in Victorian times, essentially, she put a link between carbon dioxide and warming of the atmosphere. That’s crazy.
Host: Shamini Bundell
Yes, and although she was the first person, we think, to do it, one of her contemporaries, a man called John Tyndall, published a more sort of expansive study of the same thing only three years later, 1859. But the thing is, he is the one who is really well known for being the father of this sort of global warming science and she’s been really completely forgotten.
Host: Nick Howe
This sounds like an all too familiar story, to be honest.
Host: Shamini Bundell
Yeah, so there’s a science historian called John Perlin who is writing a biography of her, Eunice Foote, and that’s why he’s been digging all this up, and his attitude is very much that the reason that her work has been ignored and she really hasn’t been remembered is because women at that time weren’t really seen as scientific equals to men. So, for example, her work was actually presented at the tenth annual meeting of the American Association for the Advancement of Science, but women weren’t allowed to present their own work so another scientist read out her work, and similarly, she had patents related to other work she was doing but the patents were in her husband’s name because women at that time weren’t allowed to defend a patent in court if they were married.
Host: Nick Howe
Wow, so she can’t even present her own science then. Hopefully times have moved forward a little since then.
Host: Shamini Bundell
Yeah, and Perlin is really keen that everyone celebrates her achievement as sort of the mother of climate change.
Host: Nick Howe
Well, I’ll certainly try and remember the name Eunice Foote in the future, and for this week, what I’ve been looking at is, well, it perhaps might not sound too surprising, but there’s a study that suggests that insect populations are declining.
Host: Shamini Bundell
I feel like I have heard this before. Insects have not been doing well for a while, right?
Host: Nick Howe
Yeah, and there have been a few studies. There was one that came out a few years ago that got a lot of press attention, came out of Germany and said that insects are really declining, but most of these studies have been quite localised, like that one was specifically in a protected area in Germany, and there’s been a lot of other studies like that. So, what this latest study that’s published in Science has been looking at trying to do is get a real global picture, and they’ve looked at 1,676 different locations across the world and long-term datasets for each of them.
Host: Shamini Bundell
Okay, so this is the super-huge version of these studies and the results – still not good?
Host: Nick Howe
Well, it depends where you are. So, they showed that there is, on average and not too surprising, a 9% decrease per decade in terrestrial insects, so insects that live on land. But they also show that there’s actually been an increase in freshwater insects, and so the point they’re trying to make in the paper is it really depends where you’re looking at and there is a bit more nuance to it, which is important because not everything is terrible and there are things that can be done. For example, the freshwater insects seem to be increasing because there’s been a lot of legislation to try and improve how clean water is.
Host: Shamini Bundell
Well, that’s optimistic, but am I right in thinking, not to be selfish here, that the terrestrial insects are the ones that pollenate all our crops and things and that’s a bit of a concern for us?
Host: Nick Howe
Yeah, I mean it’s obviously still very, very concerning and a 9% decrease in populations, considering how many insects there are and how much biomass they make up, is still huge, and it’s particularly localised in Europe and North America, and they associate it with more intensive land use so things like farming and stuff like that. So, it’s still very, very concerning, but I think they’re just trying to say that there are things we can do and we don’t have to despair. There are some populations of insects, even terrestrial insects, that are doing well in certain parts of the world, and it’s good to have that sort of more nuanced picture that you can only get with a real globalised dataset.
Host: Shamini Bundell
Well, let’s hope that the relevant authorities pay attention to this paper then.
Host: Nick Howe
Yeah, definitely, and as someone who used to study insects, it’s quite a close thing to my heart, so I hope that people start to take action. But for you listeners, if you’re interested in getting more bite-sized bits of science like that we’ve just discussed then make sure you check out the Nature Briefing, and we’ll put a link to that in the show notes.
Host: Shamini Bundell
Also, if like me, you’re a big dinosaur fan, you might be interested in a new Spinosaurus skeleton that’s been discovered in Morocco. I’ve been working on a short video about it and the research suggests that Spinosaurus, which is this big predator, had a fin-like tail which would have helped it swim and hunt, and you can find a link to that film in the show notes too.
Host: Nick Howe
That’s all for now. But just before we go, a little bit of good news. We’ve been nominated for a Webby Award. We’re shortlisted in the Science and Education Best Individual Episode category for a 2019 show in which I looked at the science of foot calluses, we learnt about protein-based archaeology and we had an on-location report on the Ebola outbreak in DRC. But listeners, we need your help. As well as the main nomination, there’s also a People’s Choice Award and understandably, we’d like you to vote for us. You can find all the details about how to do so in the show notes for this week’s episode. I’m Nick Howe.
Host: Shamini Bundell
And I’m Shamini Bundell. Thanks for listening.
