Live Long and Master Aging podcast



Sniffing pleasant smells to improve memory

Michael Leon | University of California


Memory loss is often cited as one of the most worrying aspects of growing older. But what if the section of the brain that’s responsible for memory could be stimulated by simply sniffing a few pleasant odors? There is extensive research pointing to a relationship between exposure to different smells and memory improvement.

A clinical trial led by Prof. Michael Leon at the Department of Neurobiology and Behavior, University of California, Irvine, suggests the loss of olfaction can cause the memory parts of the brain to deteriorate, while adding more smell experiences can improve memory. The research also explores the use of environmental enrichment, as it’s known, to treat neurological disorders like autism.

Prof. Leon’s team used diffusers to release various essential oils while participants slept, leading to improved memory and sleep. The results suggest that exposure to smells like orange and lemon significantly improves memory in older adults, with some experiencing a 226% increase.

Researchers have developed a device called Memory Air that automatically emits odors while individuals sleep, providing the brain with the necessary stimulation. In this interview we discuss the evidence and explore why such an approach could be valuable not only in improving memory but overall well-being.

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Connect with Prof. Michael Leon: University of California, Irvine | Memory Air | Mendability

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CHAPTERS (time stamps go to YouTube)

  • 00:00 Introduction
  • 01:15 Research showing that adding stimulation through odors improves memory
  • 02:50 Michael Leon’s story – education, research and working with rats
  • 04:29 Environmental enrichment research
  • 07:28 Mendability
  • 08:31 Visual stimulation from the natural world
  • 10:30 Olfactory stimulation deprivation
  • 12:18 Brain-healthy stimulation – exercise and memory
  • 14:11 Exposing older adults to pleasant overnight smells to improve memory – new research
  • 15:26 Critical memory Pathway
  • 16:49 Memory Air device
  • 18:58 Emotional center of the brain and depression
  • 19:45 Good smells vs bad. Do they have equal impact on the brain?
  • 22:48 Control groups
  • 24:25 How the Memory Air device was developed
  • 26:21 Is it safe?
  • 27:40 How does the Memory Air device make you feel?
  • 29:07 Wine tasting technology for olfactory stimulation
  • 31:00 Importance of odors from birth to old age

TRANSCRIPT – This interview with Prof. Michael Leon was recorded on April 2, 2024 and transcribed using Sonix AI. Please check against audio recording for absolute accuracy. (Time stamps below)

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Michael Leon: [00:00:00] We just use essential oils, pleasant plant based oils that are typically regarded as being very nice orange, lemon. We have quite a number of people saying that they feel better, they sleep better. Their memory is better. They feel happier.

Peter Bowes: [00:00:15] Can exposure to different odors improve memory? Is there a relationship between what we smell and cognitive ability? Michael Leon is a professor in the Department of Neurobiology and Behavior at the University of California, Irvine. Hello again. Welcome to the Live Long and Master Aging podcast. I’m Peter Bowes. This is where we explore the science and stories behind human longevity. Michael, it’s good to talk to you.

Michael Leon: [00:00:45] Glad to be here.

Peter Bowes: [00:00:45] When I first heard about your research, I was skeptical, to be honest. Did the findings surprise you that according to your research, we can improve memory by what is it, 226% in older people through exposure to various smells? That sounds very significant.

Michael Leon: [00:01:07] Yeah. So we weren’t surprised at all. There are probably about two dozen papers that have been published showing research that is very consistent with what we’ve found, both by showing that the loss of olfaction will cause the memory parts of the brain to deteriorate, and that adding more stimulation, more olfactory stimulation, many odors can improve the memory parts of your brain and memory. And so we are just consistent with everybody else. We did it at night so that we could ensure compliance. It’s hard to get people to do things during the day, even take an aspirin. And so we we’ve done that. And that’s given us a very high level of improvement in memory. To our knowledge, that’s the largest improvement in memory for older adults that’s been reported.

Peter Bowes: [00:02:02] So I guess the challenge is to embrace that research, your research and the other papers that you refer to that. And as you say, there has been research consistent with your findings over a number of years with different scientific institutions. So I guess the challenge is to embrace that and use it to our advantage, and especially the advantage of older people and memory challenges. I want to dive into that. Just before we do, though, just tell me a little bit about yourself and your own career history and what brought you to this point in your research?

Michael Leon: [00:02:32] Well, um, I grew up in New York City, family of very modest means, but I was very lucky in that, the city of New York had a university system that included Brooklyn College, which was absolutely free. And so I was able to go to college based on that. I lived at home. I took the city bus to college, and I got interested in doing research. Just by chance. I had a summer job cleaning rat cages, and it turned out that when I wasn’t cleaning, I could talk to the people in the lab and they were doing very, very interesting things. And so I got started and started doing research in that lab. I then went to the University of Chicago to get a PhD, and, I got out of graduate school as quickly as I could so I could go on and do research on my own. It’s only in recent years that I’ve started to do clinical research to see if we can translate the things that we found in animals in the lab, to the real world and to real people. .

Peter Bowes: [00:03:34] Well it’s interesting you should mention working with rats, because much of the research that you mentioned earlier in this area has been done in rodents research on environmental enrichment, as it’s often described. So I’m wondering, maybe you could give me a little potted history of, of the research and why it prompted you. And in terms of the findings from previous institutions, why it prompted you to carry out the studies that you’ve been doing.

Michael Leon: [00:03:58] So if you look at most laboratory animals, rats and mice, typically they’re kept in standard isolated box cages. Nothing much to do, but they seem fine. They they learn. They remember things. They have social behaviors. They have normal motor behaviors. But if you take those same animals and you put them in a much larger cage with a bunch of friends and many new things to do, so they get some novelty in their lives and much more stimulation, their brain becomes much more complex, it becomes much more capable. And they are different animals. They are completely their behavior is different. Their abilities are different. And even more impressive from my perspective, is that when scientists have produced animal models of human neural disorders, and there are a couple of dozen of these, they show their human like symptoms when they’re kept in the standard box cages, that is, with very little stimulation, but they lose many or all of these symptoms when they’re placed in an enriched environment. And that’s fascinating because if you had a pill that did that, people would be doing backflips. But no one really thought about using environmental enrichment for humans, particularly in the modern world that we live in, because people think that we’re getting too much stimulation of anything. And so we were the first to use this idea to treat a human neurological disorder. We did this with children who have autism, and we looked at seriously affected individuals. `We gave their parents a kit to take home, and every two weeks we gave them a different set of instructions. So they had continual novelty in their lives. And within six months, we found that there were dramatic improvements in their behaviors, social behaviors, focused behaviors, and all the ancillary problematic behaviors that they have problems with sleep and eating and mood. All of these things improved, and the more compliant the parents were in doing these things, the better their children became. Their sensory issues improved greatly, their IQ improved their objective. Diagnosis of autism improved. After six months, 21% were no longer regarded as having classic autism, compared to 0% in standard care. And after six months, 42% had a major improvement in their symptoms compared to 7% in standard care. So this was a major improvement. It’s now available to people around the world. The website is called Mendability. Mendability, one word, and it just allows people to start to treat their child immediately. They don’t have to wait six months or a year for a diagnosis. They can get that treatment immediately. And we also found that it works for older kids. So standard treatments really are good for just a few years. And our program is effective for teenagers. They are actually very good at at doing this with their parents and with themselves.

Peter Bowes: [00:07:13] Just going back to one thing you said a moment ago about environmental stimulation, and it kind of raised a question in my mind, are we getting too much environmental stimulation now, or actually, are we getting too little because we are confined in our little spaces and perhaps not getting out into the environment enough? I guess times are a changing, and our exposure to what’s around us is changing dramatically as well.

Michael Leon: [00:07:39] Well, there’s a great deal of information now about being in the natural world and how that is good for your brain and good for your mind, and people tend not to be doing that. They tend to be looking at their phones all the time. So they’re getting a lot of visual stimulation. They’re probably getting a lot of auditory stimulation. They’re not getting enough olfactory stimulation. It turns out you can replace the entire environmental enrichment program for rats and mice with just odors. If you give the individuals many odors on a regular basis, we call it olfactory enrichment. They have the same benefits. If you give it to older mice, their brain improves, they start producing more new neurons, and their memory improves just giving them olfactory stimulation. So we think that in our modern affluent world, we just don’t get enough olfactory stimulation. We are, in fact, probably deprived of sufficient olfactory stimulation. When you think about how the human brain evolved. It evolved at a time when nobody took a shower, ever. And so, among other things, people were getting plenty of olfactory stimulation. In these days, you know, my guess is that if you took a deep breath now, you wouldn’t smell anything. And that’s a problem, because the olfactory system has the only direct connection to the memory centers and the emotional centers of the brain. All the other senses have to go through the thalamus, which is basically the brain’s side streets. And so consequently, they have much less impact on their memory and emotional status than the olfactory system that has what we regard as a superhighway going to these areas. And so the loss of olfaction is really very important, because when you lose your olfactory ability for any reason, at any age, the memory centers of your brain start to deteriorate. And when that happens, your memory starts to go. And not only don’t we get much olfactory stimulation in our modern world, but there are many things in the modern world that also acts on our olfactory system to damage it. So toxins in the environment, smoking, air pollution, stress, childhood maltreatment, wide range of medications, menopause, Covid 19, all of these – oh head injuries. All of these things are damaging both to your olfactory ability and to your memory. When people say they have brain fog, what they’re saying is that their memory isn’t working so well, and all of these things damage the olfactory system. And we think also contribute to the loss of memory. And of course, as you get older, all of these things add up. And by the time you’re about 60 years old, your olfactory ability and your memory ability start to fall off the table. And they continue to go hand in hand through the rest of your life. And so after that point, people start complaining about they can’t remember where their keys are or they can’t remember where they were, why they walked into that room. But what they don’t realize very often is that they’ve also lost their olfactory ability, because when you lose your olfactory ability gradually, most people don’t realize it. When you lose it abruptly, as people did in Covid, then everybody realizes that it’s a problem and they complain about it because they can’t smell anything and they realize it. Whereas people who lose it gradually simply don’t know that they’ve lost it.

Peter Bowes: [00:11:13] So what you’re talking about here, I’m going to put this in very simple terms, in terms of the way that the brain works and the way that you could say everything is connected, the brain, the body, and your ability to detect smells and respond to those smells. They are intrinsically connected with the way our body functions in many, many other ways. And memory is just one of those functions that indirectly is related to our ability to detect smells and to respond to smells.

Michael Leon: [00:11:42] Yeah. So it turns out that your brain needs a great deal of stimulation, and when it doesn’t get it, it starts to deteriorate. It’s just like your muscles, right? If you don’t use your muscles, they start to deteriorate. If you start using them regularly, they build up. And unfortunately, if people would exercise more, they would get more stimulation. And by now everybody knows that exercise is good for you. You know, if it were a drug, it would be a miracle drug. The problem is, is that particularly among older adults, only about 15% of older adult men and about 10% of older adult women do even the minimal amount of exercise that’s recommended. And so while exercise is great, it’s just not effective because people don’t do it.

Peter Bowes: [00:12:31] So let’s dive into your most recent research and the experience that you’ve been doing with older adults, introducing a range of smells. And you mentioned that this is done overnight, very difficult to get people to do these things during the day. But just explain to me the methodology, in other words, what you did with these people, how many they were, who they were, how old were they, male or female, and the kinds of smells that you introduced to them and the impact of that.

Michael Leon: [00:12:58] So we just used essential oils. These are just pleasant plant based oils that are typically regarded as being very nice orange, lemon, you’d smell them and you’d go, oh, that’s that’s pleasant. We put them in a diffuser and we had different bottles full filled with these things. So every night they put in a different one of these things, and for two hours they were exposed while they were sleeping. It was, uh, easy to get them to do it. They were very interested in getting their brains imaged, which I thought that this might be difficult to get people to do, but it was actually a feature rather than a bug. They wanted to see their brain image we used. We used MRI and we found that the critical memory pathway in the brain changed to about the same extent as the memory did. And so both the brain and cognitive behavior showed us the same thing.

Peter Bowes: [00:13:54] You said critical memory pathway. Can you just explain in layman’s terms?

Michael Leon: [00:13:59] So I’ll tell you what it was called because no one will remember it, but it’s the uncinus fasciculus. And it’s a critical pathway between different parts of the brain that are involved in the in the production of memories. It was striking to see such a similar response in both the brain and behavior. And there’s another group that actually found something I think, just as remarkable, maybe more remarkable. They reported that when they had demented older adults, they were able to give them olfactory stimulation and very rapidly get an improvement on five standard memory tests with improvements up to 300%. And that makes it the most effective treatment for dementia that’s out there. There’s nothing even close by a mile. And of course, in addition to being effective, it’s also completely safe. It’s completely affordable. The problem is that it wasn’t convenient because they needed to use 40 odors twice a day to get this done, and very few people are going to do that, particularly people who have memory problems. And so we’ve devised a device, we call it Memory Air. It produces 40 odors twice a night. As you’re sleeping. You don’t even have to press a button. It does it automatically. It sits on your nightstand, blows the odors as you sleep, and people will be able to get the kind of stimulation that their brain probably needs, and they can now get that from us. Memory Air. The place to find it. 

Peter Bowes: [00:15:36] Yeah that’s interesting. And it really prompts my what was going to be my next question, because you mentioned initially people just being exposed to one particular smell, one odor for a couple of hours during an evening. Can you just extrapolate on that then? So it was a different odor every night over what time period did you do this and what age were these people?

Michael Leon: [00:15:56] So they were 60 to 85. And both men and women, they were all locals, Orange County, California, and they all had signed up to because they were interested in joining, being recruited into a study that would improve their memory. And so we were able to recruit quite a number of them. Unfortunately, the pandemic came in and stopped us from bringing people into the clinic, and so we had a smaller study than we hoped. We will be replicating this study with our device, with a couple of hundred people to show that it works with many more people. People were very attracted to this idea, all of them. We gave them the option of keeping the devices, and they all decided that they wanted to, and they most of them continued to use the odors. You know, after we were done with the study, many of them reported that their sleep improved. People who got the olfactory stimulation slept 22 minutes more a night than the people who didn’t. And so we think it improves sleep as well as everything else. One of the things that is remarkable is that it, not the olfactory superhighway, not only goes to the memory centers of the brain, but it also goes to the emotional center of the brain, the amygdala. And there are now three studies showing that you can decrease depression symptoms by giving olfactory enrichment. And so we think there’s going to be a use for olfactory enrichment for depression as well as for memory.

Peter Bowes: [00:17:36] You mentioned these smells are generally positive. They are pleasant smells, orange, lemon. Does it matter whether it’s a pleasant smell or an unpleasant smell to stimulate the brain?

Michael Leon: [00:17:50] We don’t know, because we are not brave enough to give people bad odors to put in their bedroom. That’s actually been a problem in both in the basic literature and in the human literature. People don’t want to use bad odors, their aversion. And so we don’t know that much about it, both in terms of its coding and its effect on individuals. It’s also the case that odors that some people regard as bad are not regarded as bad by others. So if you’ve grown up with living in a place where mice are dying in the walls all the time, you regard cadaverine as a very pleasant, sweet odor. And so the military actually tried to develop a bad odor that would disperse crowds, and they couldn’t find a universal bad odor that everybody would find diverse and run away.  

Peter Bowes: [00:18:48] That’s interesting.

Michael Leon: [00:18:49] Yeah. Bad odors are just not well understood. And they are probably very powerful though. But we don’t know whether they can yield a benefit for people.

Peter Bowes: [00:18:59] Yeah. I mean, logic would tell you that, let’s say a burning smell, an acrid smell, may well provoke a response that is instinctive, that you want to get away from it, that you are alerted to a danger.

Michael Leon: [00:19:13] Yeah. And so humans actually have a respiratory reflex in response to both good odors and bad odors. So if you give people a pleasant odor, the information goes to the part of the brain that controls respiration, and you instantly start to increase your respiratory rate. You start sniffing even if you’re not doing it consciously. On the other hand, if you give people a bad odor, the olfactory, the respiratory center stops you from sniffing, right? It just cuts off the odor as soon as it can. And so this happens even when you’re sleeping. At the same time, because the odors don’t go into the thalamus. The thalamus has all these connections to the brain sleeping centers. That’s how you can wake up. So an alarm clock gets a sound, goes to the thalamus, goes to the sleeping wake you up. Tactile stimulation can do the same thing. Bright lights can do the same thing. That’s why you turn off all the lights. But you can’t wake people up with an odor. Because it doesn’t go through that system. And so people tried to make an olfactory alarm clock to wake up deaf people. Right. And they haven’t been able to do it even with the odor of frying bacon. And so people are responding to the odors, but not in terms of waking them up while they’re sleeping.

Peter Bowes: [00:20:39] In terms of the experiments that you did, how did you devise the control group? Because clearly these elderly people knew that they had a device next to their bed that was presumably emitting an odor because they set it up? Was there a way of measuring people who perhaps didn’t, didn’t know what kind of odor was being emitted by the device?

Michael Leon: [00:21:02] So what we did was we had two groups, and people were assigned randomly to each of the groups. One of the groups we called a high concentration or high dose group. So they got the diffusers with the essential oils in them and they were exposed to those. The other group, the control group, was given a low dose group. And so we put a very tiny amount of odor into their diffusers. And so we we told people that we wanted to see which one was better. And so the low dose didn’t give much response as you would expect, whereas the high dose did. And so people weren’t sure when they weren’t smelling whether they were just getting the low dose or whether there wasn’t anything there, but there was something there. It just wasn’t very high.

Peter Bowes: [00:21:52] So there wasn’t the sense that those that had the low or verging on zero smells emitted thought they were getting a higher dose and responded appropriately, that you saw a distinct difference between the two groups.

Michael Leon: [00:22:07] Yeah, it’s a striking and large difference between the groups. And so it was clear that a phenomenon of people imagining that they had it and improving didn’t happen.

Peter Bowes: [00:22:18] So tell me a little bit more about the device that you’ve now developed. You mentioned a moment or two ago, which is, I think you said available now to people if they want to.

Michael Leon: [00:22:27] So people can go to Memory Air and sign up and get one. So, you know, it was actually a very difficult engineering problem. It was our third group of engineers from different companies that finally figured it out. It’s important not to have liquids because liquids spill and get all over the place and are hard to control. And so we just started working with a great group of engineers that we found, and they are doing, you know, they did a great job in figuring it out. And there were a lot of pieces to this thing, 40 odors with different characteristics and different ways of of dealing with these different characteristics turned out to take quite a while. It took about four years to develop. It’s now working and it looks great and works great.

Peter Bowes: [00:23:20] So if just to clarify, if there are no liquids involved, there are no essential oils?

Michael Leon: [00:23:26] Ah. So we take the the liquids and we take the natural odors and embed them in wax. It’s a special kind of wax that we we figured out. And all the odors go into this wax-like substance. It’s then covered with another mesh that doesn’t allow the wax to escape. And when we heat the wax, the odor comes out, a fan pushes it out toward you. And we can do that 40 times, twice a night.

Peter Bowes: [00:23:58] Some people might be wondering about the safety implications of this. What kind of factors have you looked into and any possible negative side effects?

Michael Leon: [00:24:08] Yeah, we haven’t found anything. People have been using these odors for centuries. And so these are given at a very mild dose. It’s important not to accumulate the odors because if they’re just sensed as a single odor it doesn’t work. They have to have individual odors. And so the safety really isn’t a problem. The FDA is giving us a pass. They regard this as being quite safe. There’s a category called generally regarded as safe. And all of these odors are are are on that list. We haven’t had any problems either in our studies or from the many, many people who use these things.

Peter Bowes: [00:24:51] And from those people that have been using it anecdotally. What are they telling you in terms of the impact? Is this an impact that they can appreciate and and realize immediately over a period of days, or is it something that is going to take a few months before and in fact, do they feel it, or is this something that’s happening, that an improvement that’s happening in their brain that may be fairly subliminal to start with?  

Michael Leon: [00:25:15] So you know, you can’t really trust people because they can imagine things that don’t exist. But, you know, we have quite a number of people saying that they feel better, they sleep better, their memory is better. They feel happier. You know, we have people who’ve had PTSD who say that they no longer have nightmares that wake them up and cause a great deal of trouble for them. So we get a lot of comments saying that they like it. And the fact that people continue to use it is indicative of something that they think is good. But in addition to that, we are developing a memory test for people to take online so they can take a baseline test on our website. And then every six months, they can take another test to show objectively that their memory has hopefully improved. 

Peter Bowes: [00:26:10] What does it cost, Michael? And are there maintenance cost implications as well?

Michael Leon: [00:26:14] Yeah. So the device calls costs $799 and the monthly odor belt costs $39. And we’ve had about 10,000 people sign up to get it even before it was available.

Peter Bowes: [00:26:30] Are you using it yourself?

Michael Leon: [00:26:32] So I’ve been doing olfactory enrichment for quite a while. I’ve used a sommelier training kit. So sommeliers, as you know, are professional wine tasters, actually professional wine smellers. And they trained by sniffing dozens of these odors every day so that they can learn to identify odors in fine wine. And in order to to do that, a company has developed a set of odors that you can just sense in your spare time. So I’ve been doing that for quite a while. Master perfumers trained the same way. And in both cases, they’re the memory centers of their brain has increased in size because of their activities. So I’ve been doing it for quite a while. It’s pleasant, I think, helpful, and I’ll continue to do it using the Memory Air device going into the future.

Peter Bowes: [00:27:25] Well, Michael, I think it’s really interesting. I’ll put a link to your original research into the show notes for this episode, also to your website. There’s also a transcript of this conversation as well. I’m just curious in ending this, we talk a lot about human longevity on this podcast, the aging process, which you’ve talked about during this interview a couple of times. Based on your own research and what you found, and you say that you’ve been practicing this for a long time yourself in terms of exposure to different smells, how do you see your own future, and how do you see this kind of research developing, perhaps as an intervention to help us age better and potentially live longer?

Michael Leon: [00:28:11] So I think people who live in our modern, affluent world probably need this kind of stimulation from birth. We have preliminary data showing that we can improve executive function, which is basically IQ and focused attention in school children. We think that there’s a great deal of interest in just young adults and taking it. And of course, people who are older are really desperate to find something that can maintain their memory or restore it. And so I think that we’re going to find that we’ve been depriving ourselves of odors. And while that’s been very good in cleaning up the world and making the modern world a pleasant place to be, it also has probably been a problem for our brains. And the good news is that it’s going to be fairly easy to restore that stimulation by giving olfactory enrichment to yourselves. It’s something that I think people can do has been enormous interest. The report that we published has now been viewed by almost 350,000 people, which is, you know, a thousand times more than most publications get. People realize that this is something that attracts them. I think it’s no coincidence that people are drawn to pleasant odors. So if there’s a pleasant odor, you’ll go and sniff it. And I think it’s because we’re wired to get a lot of odors into ourselves. And without it, you know, our brain will deteriorate. And so this is just an easy way of getting the exercise that your brain needs without having to do anything.

Peter Bowes: [00:29:56] I can see why there’s been such a huge interest and a huge positive response to this, Michael, I appreciate your time. I’m going to follow this research with a tremendous amount of interest myself. Michael Leon, thank you very much indeed.

Michael Leon: [00:30:08] It’s been a pleasure. Thank you.

The Live Long and Master Aging (LLAMA) podcast, a HealthSpan Media LLC production, shares ideas but does not offer medical advice. If you have health concerns of any kind, or you are considering adopting a new diet or exercise regime, you should consult your doctor.

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