They also found among people who got the cold, if they had more hugs the cold, by that objective measures that I mentioned, that the nasal congestion and mucus was kind of less severe. So maybe it's the fact that, you know, if you do get infected, and you do end up getting a cold, it seems like the more support people have, and kind of this touch, kind of the less objectively severe the signs of illness work.
Welcome to the Stress Puzzle, where we explore the latest in stress science and consider how the science may translate to our daily lives, or where we might have missing pieces for actually making that connection. I'm your host, Ryan Brown, and I'm a social health psychologist working with the Stress Measurement Network, which is a team funded by the National Institute on Aging and includes internationally
recognized stress experts from UCSF, UCLA and Yale. Today, I'm joined by Dr. Aric Prather to chat about why we get sick at the holidays. We discuss some of the incredibly cool and foundational studies where they experimentally infected folks with the common cold, and discuss what we've learned from those studies about stress, social experiences, immunity, and illness. So, I hope you enjoy this very special holiday episode of the Stress Puzzle.
Dr. Aric Prather is a professor and Pritzker Family Fund endowed chair in health and community in the Department of Psychiatry and Behavioral Sciences at the University of California San Francisco, where he co-directs the UCSF Aging, Metabolism and Emotion center, is the director of the UCSF Center for Health and Community ,and Associate Director of the Stress
Measurement Network. Aric's research is focused on links between sleep and health, particularly immune health, and his work is regularly featured in The New York Times, NPR and the Today Show. I had the extreme joy of working with Aric as my mentor when I was a postdoc at UCSF, and so I'm especially excited that he could join us today to talk about why we get sick around the holidays. Welcome to the Stress Puzzle, Aric.
I am so excited to chat with you about this topic. Oh my gosh. I am so excited to be here, and, you know, really thrilled to to be a guest on kind of these really incredible episodes you've you've really done such an amazing job kind of leading this podcast, and really excited to be a part of it.
Thanks for those kind words, Aric. I really love this topic because, you know, as people who are broadly interested in the field of psycho, neuro immunology, so much of our knowledge base for links between stress immunity and illness come from studies like the Pittsburgh common cold studies. And you were actually in Pittsburgh as a graduate student and able to work with Dr. Sheldon Cohen, who led the
Pittsburgh common cold studies. Can you give us an overview of what you took away from those studies as your foundation for understanding links between stress immunity and illness?
Yeah, absolutely. I mean, I was so fortunate to be kind of there while these studies were ongoing. In total, there's five common cold studies, starting with the common cold unit in the UK. So, that was kind of a British Common Cold study, and then kind of subsequently moved to Pittsburgh and were carried out in succession, four of them in
total. And so, I was there for the fourth one. And as you said, I got to work with Sheldon over that time, along with kind of many other luminaries in the field of psychoneuroimmunology. And so, it was just such an exciting time to kind of live, live, the research. And so, you know, what's unique about those projects are, I think, the fact that it's really an experimental
paradigm of an in vivo immune challenge, right? So, usually in psychoneuroimmunology, we tend to really be reductionistic in how kind of psychological or behavioral factors impact specific parts of the immune system, right? So, we may be interested in kind of the increase in how T cells divide, or the activity of natural killer cells under certain
conditions? But, you know, exposure to a live virus and then what happens and who ends up getting sick and who doesn't is a culmination of various aspects of the immune system that has real clinical relevance. And so, you know, the way these studies were conducted, it was very rigorous and controlled, you know, to really try to kind of isolate infection and kind of the development of what was a biologically verified cold. And so, if you'd like, I can just
kind of briefly describe the design, ifthat makes sense. What do you think? Yeah. So, so, I mean, again, there's been kind
Yeah, that'd be great. of several different iterations of this, but in general, you know, everyone is healthy that's brought into the study. I mean, they go through kind of robust screening process, right? So, you know, in that way, it's not necessarily fully generalizable,
right? Because everyone is really healthy when they come in, they all get a blood draw at the beginning, before they're exposed, you know, several weeks before they're exposed in this experimental setting to account for their immunity against that virus, right? So, you know, most of us, if not all of us, have been exposed to things like. The rhinovirus, the common cold, and
so we've kind of built up immunity at varying levels. And so, it's really important to account for that when we're doing the analysis of subsequently, everyone fills out questionnaires, things like about the amount of stress
they're experiencing, the amount of social support. In some of the studies, they undergo telephone interviews for two weeks, you know, things that like, ask about people's daily activities, the types of stressors they experience, kind of, you know, tensions or conflicts, social support that
they might experience. Me, I think one of the more interesting projects that is really relevant to this discussion about the holidays is the role of hugs as a mechanism for social support and protection, and so, that, you know, that kind of stuff was measured by thes telephone interviews. And then, people come into the laboratory, they're exposed to the live rhinovirus, and then they're
quarantined. And during this, this quarantine period, which varies by study, but it's usually between five or six days, they at this time, they were quarantined at a in a hotel in Pittsburgh, and then they kind of underwent a variety of observations, right? So, people would report on whether they felt sick and kind of symptoms of that sort. But it was really important to try to isolate more objective measures of illness.
And so, you know, people went through nasal washing, so that the washing could then be cultured to see if the virus was replicating and if it was that was evidence of infection. But then, they also went through kind of these objective measures of symptoms. So, one was to have them collect their tissues throughout the day. So, you know, as we all do when we when we have the a cold, we have increased mucus secretion. And so, they would, you know, use their tissues and collect them.
And then, a research assistant at the end of the day would collect all those tissues up, put them in a bag and weigh it, right? And so, you subtract out the weight of the bag, and you subtract out the weight of the tissue, and you get an objective measure of how much mucus was produced on that day. My favorite detail of these studies.
And then, and then, the other one is, is, is one of a measure of nasal congestion. And so, each day, people would put their head back, and we would, they would put a dye into their nose, and time how long it took to get to the back of their throat, so you could kind of visually see it, but also it has a taste to it, so people could taste it when it got into their throat and and kind of the longer it takes, can
the more congested someone was, right? So, you have kind of this, this whether someone's infected or not, and then if they were infected, if they met a criteria that had been, you know, developed over time and doing these studies, kind of a threshold for a mucus secretion or nasal congestion time, they were deemed to have a biologically verified cold,
right? So, kind of, all of this happens, and then in the end, the outcomes of these studies are kind of whether you're infected, yes, no, and of those who are infected, yes, no, who has a biologically verified cold? And what it's told us has been kind of, kind of transformative in our understanding of psychological and behavioral predictors of susceptibility to infectious illness. So, what have we
learned? Right? It really has told us so much. I think kind of the standout findings that have been replicated over time is stress, right? So, people that have higher perceived stress, more chronic stressors, interpersonal stressors, all seem to have kind of a dose dependent effect on susceptibility to infectious illness, right? So, meaning, the more that you have, kind of the more likely you are to be
someone who develops a biologically verified cold. And so, you know that obviously has implications for things like the holidays or any kind of stressful event where kind of our lives are disjointed, even even things that are exciting, right? Because, you know, our immune system is certainly impacted by, you know, high stress events. Good news is that we've also learned that things like social support can buffer
these effects. So, you know, if people have high stress, but they also have high social support, so kind of connections within their community, feeling like they're emotionally supported. That seems to buffer that impact. And I mentioned it earlier. I mean, one of, kind of the most interesting studies just given kind of this, this focus on the holidays, is the study around hugs, right? So, you know, who doesn't like a good hug? Not everyone. But you know, certainly you know, it
does make me feel supported. One of these Pittsburgh cold studies, they did measure, kind of over 14 days, kind of how much people had interpersonal conflict, and then how much, how many hugs, you know, percentage of the week, or percentage of the days did they have hugs, right? And, and what you what they found was where, where it really seemed to play a
difference, is in whether someone was infected, right? So, what they found was that, as expected, when people reported more social support just by questioning her, this seemed to buffer the effect of kind of interpersonal attention on whether someone actually got infected. And again, importantly, everyone is exposed to the virus, right? Everyone gets the same amount of virus into their nose, but not everybody gets infected, and it turns out that social support
seemed to play a role. Interestingly, though, again, they found that the percentage of hugs also led to a lower likelihood of infection. And like perceived social support, and potentially explaining some of those effects was if people, even if they had interpersonal tension in in their life, but they also had a higher percentage of hugs during that same time period. They were also less likely to become infected.
And then finally, they also found among people who got the cold, if they had more hugs the cold, by that objective measure that I mentioned, that the nasal congestion and mucus was kind of less severe. So, you know, maybe it's the fact that, you know, if you do get infected, and you do end up getting a cold, it seems like the more support people have, and kind of this touch, it's kind of the less objectively severe the signs of
illness were. And I thought, I just think that's really kind of a nice thing to think about, because one of the challenges that we have around the holidays is we're around more people. You know, we might be in more closed settings, particularly in the winter, and so we're likely to experience more exposures, right? And so, it's nice to think about what types of things might actually be protective, given that we may not be able to control the exposures.
That's a great point. And I love that you've emphasized all of the different sort of ways that you can look at both the likelihood of infection, the symptom experience and and does it turn into a clinical cold. So, these studies really gave us such an incredible foundation for thinking about these acute illness models. And you know, like you're saying, thinking about stress and health and this
timing of the year. You know, when we turn to the holidays, specifically, we know so much goes into our stress and joy around the holidays, where we might be recovering from the semester or year of work or school, experiencing colder weather, seeing family you may not have seen in a long time, having kids who are sick, traveling, disrupted routines,
and, you know, so much more. So, I'm kind of thinking we can take a dismantling approach, almost to thinking about being sick at the holidays, and tackle how each piece of the holiday experience might contribute to greater susceptibility to illness or worse symptoms. So, starting with the experience of stress itself, can you talk through why we get sick when we're stressed or in the time when we finally have to relax after being stressed?
Yeah, absolutely. So, when we think about kind of the mechanisms through which stress may impact the immune systemand susceptibility to, say, upper respiratory infections, you know, it's generally falls into the bins of, okay, what are the biological processes that are impacted by stress, and how do those impact the immune system? And then, what are other factors that may play a role, like
health behaviors, right? And, you know, we certainly don't want to discount those, because obviously, when we're stressed,
you know, lots of things change. You know, as as as you said in the beginning, Ryan, you know, I study sleep, and certainly that can be disrupted, and we know that that has direct impacts on the immune system, things like physical activity, our nutrition, you know, if you think about the holidays, how our nutrition may change, I mean, with respect to kind of the types of foods that we eat
May change.
May change. You know, you know, people tend to know potentially celebrate with, with substances like alcohol, that that also have impacts on the immune system. So, all of those things are going on, right? You know, when we do these types of studies, we absolutely have to try to account for those the best we can, statistically or in, in the case of the this cold study, you know, actually making it a
rigorous experimental design. And so, you know, there, there are some inklings of like, what are the biological mechanisms, particularly coming from these, these studies, and I think one of the ones that has, you know, really popped out has been the role of the neuro endocrine system and the release of cortisol, right? And so, you know, I know this has probably come up on the podcast a lot, but it really has been this interplay between cortisol and its inability to regulate kind
of inflammation, right? So, you know, we know that steroids are really important for kind of suppressing the inflammatory response, right? If someone has an asthma attack or or some kind of allergy, they often get steroids that we know can dampen
down the inflammatory response. One of the challenges that we see when people are stressed a lot is that it may not work as well over time, and so there has been evidence in these cold studies, specifically, that people that have chronic stress may develop something called glucocorticoid resistance, meaning that you're pumping out cortisol, because that's what the stress response does, but its regulatory function on
inflammation is impaired. And so you know this, this is one way, because we know that inflammation plays an absolute role in driving the severity of symptoms. In fact, you know, studies from this Pittsburgh cold study, I mean, I talked about, kind of the nasal washing, one of the things that they've done also is collect that to assay those nasal washings for pro- inflammatory cytokines, the ones that have popped out have been kind of the ones you that usually think of
when you think of inflammation. So, things like interleukin 6 or IL-6 , IL-1 and 8, all of those play an important role in inflammation, and it has seemed that IL-6, particularly in nasal washings, has been one of the strongest predictors of the severity of someone's cold response. So, if you imagine that people are stressed, they are developing, you know, producing higher levels of of cortisol over time, but that cortisol just is not doing what it needs to do, it may, in fact,
leadto more severe experiences of respiratory illnesses. And so, that, you know, that seems to be kind of one of the the primary mechanisms in trying to understand what's going on with the immune system here. I mean, other, you know, of course, the immune system is incredibly complex, and we often are kind of at the mercy of what tools we have to understand this very dynamic and kind of maybe temporally specific process, but it is. It is giving us some idea of what the mechanisms are.
Awesome. And just because we're talking about the Pittsburgh Common Cold studies, so much, I wanted to emphasize to anyone early career or trainees that this data is also available online, so you can if you're interested in using this datafor a class or papers or anything like that. It's a really awesome health psychology based data set, and you can look across multiple of the common cold studies. So, just to plug that real quick.
Yeah, I mean, thanks for doing I actually always try to do that. So, it's, it's on the Carnegie Mellon University website. So,it's, cmu.edu-common-cold-project, and all of the data is available, so yeah, please take advantage of it, because there's so much more to learn.
Perfect, yeah, and we'll link that in the show notes as well, so you can use that for anything, and it's such a wealth of data. And you alluded to this earlier, but you know, we have this combination of potentially dysregulated immune system, and then we also likely have a greater risk of exposure to pathogens when we're traveling and encountering more strangers and friends and family and enclosed spaces. So, how do you think about the increased risk of exposure throughout the holidays?
I think of it as, you know, a real a real problem. I, you know, I talk to a lot of people about these types of studies and kind of the work that we've done in the context of the Pittsburgh Common Cold projects. And, you know, I always say that, you know, we we find all these predictors of colds' susceptibility, but probably the biggest predictor is exposure, right? So, I mean, I think exposure is, is, is part of life, and you have to try to mitigate it the best you can.
You know, obviously there are factors that can prevent this, things like hand washing if you're ill, potentially wearing a mask. You know, being mindful of close spaces around people who might be sick. But you know, like, luckily for many of us, our immune systems are fairly robust, and for those that don't have a robust immune system that are immunocompromised,it's really important to take particular care and be careful around those that have those challenges to their immune system.
And then, coming back to the sort of disrupted routines and health behaviors throughout travel and especially around the holidays. Now, we're really in your sweet spot. So, what can you tell us about how sleep affects immune health? And you know, I've heard you emphasize, and I am re-emphasizing this to myself through the holidays, that one bad night of sleep doesn't make or break our health, and you
know how worry can maybe make it worse. So, I'm curious how you think about sleep and disrupted routines through times like the holidays?
Yeah, there's a lot of opportunities for disrupted sleep in the holidays, right? From kind of kind of events that might be atnight that kind of shorten you on, on opportunity for sleep traveling and kind of changes to your circadian rhythm and dealing with jet lag, all of those can lead to poor night's sleep. I mean, experimental studies of kind of sleep deprivation certainly support acute effects
on kind of your immune functioning, right? So, so there are studies showing that when you deprive people of sleep compared to kind of healthy sleepers, you know, their T cells don't divide as well. When challenged, as I mentioned, your natural killer cells don't, don't kill off things as well. You may have increases in kind of inflammatory processes that you know might impact other aspects of your immune system.
But, and then, I think, you know, maybe the most convincing outside of the Pittsburgh Cold studies, where we also find that people who are, you know, short sleepers, on average, are also more likely to develop a clinically verified cold after accounting for things like stress and social support and all these other factors, is the impact on on sleep and
vaccination response. Where we, youknow, across a range of different studies have found that kind of people who are not sleeping well, particularly those are kind of chronic short sleepers, don't seem to kind of respond as well to these inoculations, these immunizations, which, of course, will put you at risk if you are again faced with things like the flu and other things that are out there that you know certainly are challenging to your immune system around the
holidays if there's extra exposure. But, I think you're also right that, you know, one bad night of sleep isn't going to make or break your health. I mean, they're, of course, the model that we think of is like, well, maybe it does, if you're
exposed right away, or something like that. But, you know, I mean, I think usually focusing on on your sleep and and getting too round up in that can actually create kind of a cycle where, you know, you you don't sleep well, then you're really stressed about the fact that you're not sleeping, you're more susceptible to stress, and then that feeds into your night. And I think, you know, it's really important to, you know, make sure that sleep is a priority. But also, you know, there I take
the perspective that we sleep to live and not live to sleep. So, you know, just trying to manage the best you can and and make it a priority, and know that all of these things are interrelated, and do your best to protect your immune health.
Yeah, and then, you know, knowing you're not immune to any of these pieces, how do you think about your own routines throughout the holidays? Are there any specific routines that you try to maintain when you are traveling?
Yeah, you know, I mean, like it like everyone, we're all kind of doing our best right and kind of taking things as they come. And I think, I think it's important to try to prioritize these kind of clear health behaviors that we know are helpful for supporting immune health, trying to be consistent with for me and my family, with respect to, like, bedtime routines and taking time out for yourself to try to
manage stress. I mean, you know, everybody's holiday experiences is different, and some are kind of more pleasant than others, but that, you know, they're always kind of rife with complexity, especially around people that you maybe don't see all the time and may have differing views. And I think it's important to try to go in with the mindset that you know things are not going to be necessarily easy, but that you
have the resilience to get through it. And then, you know, being careful to take time out for yourself, to be kind to yourself, to kindof help fill the tank when you know some of these holiday experiences can be draining, and you know, based on the data that we described here may have an impact on on your health and well being. And so, I think, you know, being kind to yourself, being kind to others, trying to manage your time the
best you can is really kind of the name of the game. And really try to find the joy in this togetherness that we may have over this holiday season.
I completely agree. And I think, you know, for me personally, something that is also helpful to think about is just how the sheer disruption of all of routines changing, and maybe short, shorter sleep than usual, how that's affecting how we respond to other people, right? And so, just thinking about giving other folks grace and our reactivity to, you know, holiday conversations that might be difficult, so just taking that pause before reacting and remembering that we're herefor
community and family and all of those things. And so, I'm curious if you have any tips for managing family or friend related stress at the holidays?
I think you're right on that. You know, it's important to realize that all of us are kind of going through something and kind of trying to manage things as best we can. And so, you know, when we think about like, you know, we've done research on on sleep and stress, right? We've done a lot of work, kind of doing daily diary studies of people sleep at night
and they're stressed during the day. And, you know, we consistently find that when people get less sleep than theyusually do, they tend to kind of experience more severe stressors. They impact them more, and people are kind of short on the ability to regulate their emotions. And all of us have felt that experience where you know you're like, a little bit more on edge, or you're a little bit more crabby, and you
know you can understand why that's happening for you. But it's also important to realize that there are other people in the in kind of your collective network, that are also experiencing those things, and the more that we can kind of be mindful of that and and try to kind of, as you said, kind of
provide some grace. That's that's what I try to do. And then I again, I also try to kind of build in time to rejuvenate and kind of restore that emotion regulation capacity that might be shorted given the circumstances.
Yeah, perfect. We've addressed this in a couple of different ways, but I'm curious if there's anything else that
I mean, I think the first thing is, and I know this has come up in other episodes that you know, stress isn't necessarily bad, right? You can certainly kind of experience it as a challenge rather than a threat. And I so, I think that's a really important way to shift your mindset around the coming holiday season. But then again, you want to kind of overlay andand these other health
strategies that can be supportive. So, indulging in the social support during this season can be clearly effective in preventing some of these negative health consequences, you know, ensuring that you kind of keep your health behaviors in check, and like, just try to find the joy and meaning in these events, you know, I found myself more recently, making sure that I don't let work get in the way of things with my family. And I've had people say, Oh, well, you can't make this
meeting. I said, you know, it was on like Halloween, for instance, and I was like, there's only so many, you know,
we only get so many of these. And you know, that has been perspective that I've taken that has really helped me give myself allowances to enjoy these events, because, you know, as we've lived through a pandemic and all these other things, time you're thinking in terms of recommendations you might give is is a resource that is finite, and making the best of the people generally to support their health throughout holidays, I think, is really important. stressful holiday seasons?
Absolutely. Picking up on what you said there. I you know, my goal, going into this holiday season, I think is going to be to lean into exactly what you were saying there, so indulging in the social support and just leaning into the joy and meaning of this holiday season. So, thanks so much for joining us for this very special holiday episode of the stress puzzle. Aric.
Thank you and happy holidays.
Thanks for tuning in to this episode of the Stress Puzzle. We'd love to hear your thoughts and feedback on any issues we've covered today. You can email us at [email protected] and you can also send requests for topics or guests for future episodes. The best way you can support the show is by leaving five star reviews wherever you listen to our podcast and sharing with your friends or your collaborators. And until next time, we're wishing you good stress and opportunities for rest.