My mother always tells me to bundle up before I go outside during the winter, because otherwise I’ll “catch a cold.” When I first learned about the germ theory of disease, I thought she was wrong. Cold doesn’t make you sick, I thought. Germs make you sick.
Recently, it’s become obvious that I was wrong and she was right. Germs are responsible for disease, but it’s crucial to remember that germs are everywhere. Our immune systems are constantly fighting these microscopic invaders. In fact, we’re probably infected with the common cold to some extent even when we don’t show any symptoms.
During the flu season of 2005, an experiment was performed to test the idea that being cold can make you sick. 90 people kept their feet in a bowl of ice water for 20 minutes, while a control group of 90 people put their feet in an empty bowl for 20 minutes. Over the next 5 days, 29% of the group with chilled feet developed cold symptoms, compared to only 9% of the control group.
Professor Eccles explained this effect by saying that our bodies restrict blood flow to the extremities when we get cold to help conserve body heat for the torso and brain, which really need to be warm. Cutting off the blood flow reduces the supply of white blood cells which are the immune system’s primary weapon against germs.
While his explanation makes sense, there may be a more general effect at work. The human body is a machine that accepts fuel in the form of food, and uses that fuel’s energy to keep us warm and to power our immune systems, muscles and brains. However, in frigid conditions our bodies have probably evolved to say “who cares if I might get sick a week later when I’m going to die of hypothermia in half an hour?”
In other words, the optimal survival strategy during bitterly cold conditions is probably to divert all the energy normally used by the immune system into keeping our bodies warm. Mammals whose bodies didn’t make this sacrifice weren’t as susceptible to disease in the long run, but that didn’t matter because they dropped dead of hypothermia before they could enjoy their good health. So that survival strategy would be eliminated by natural selection.
Anyway, the point is I was wrong, and my mother was right. Sorry, Mom!
Last modified February 6th, 2012
I was always pretty much with your mother on that. It’s pretty obvious that there’s no more reason to get a cold in the winter than the summer, if all you’ve got to go on is Pasteur.
But some seasonal diseases are still hard to explain. For example, why do flu epidemics come mostly in the winter? Moreover, why are there successive waves of mutated flu viruses that sweep around the world each winter?
My personal favorite explanation has always been the Pigs in the House theory. (Ok, maybe it’s my favorite because I made it up.) That is, when it gets cold, people bring farm animals into their houses, or barns immediately adjacent to their houses. This allows the viruses that like to migrate between humans and domestic animals to start an infection cycle that then sweeps the world, thanks to modern methods of rapid travel. Of course, people in the U.S. and Europe don’t bring their animals into their houses when it gets cold any more…but people in poorer, more backward countries–like China–do. That’s why flu epidemics come from “Asia”. Well, it makes as much sense to me as any other explanation I’ve ever heard.
To reply to my own comment…do flu epidemics come in the “summer” (i.e. same time as our winter) in the Southern Hemisphere…or do they coincide with colder weather. Facts are urgently needed here…
According to the Wikipedia article on the flu season, there are actually two flu seasons each year for the Northern and Southern winters. In fact, the World Health Organization produces two different vaccines every year– one for each flu season.
I thought the winter flu season could be explained by a combination of my “energy diverted from immune system to body heat” idea and the fact that people stay indoors more in the winter, allowing viruses to spread more easily. Lower humidity during the winter may be a factor too. Now that you mention it, Pigs in the House probably plays a role in less developed countries. But your question got me thinking, so I did some googling that led me to this article which reports on research performed in March 2008.
Apparently, the influenza virus which causes the flu has a special protein coat (a protective “shell” around the infectious DNA “payload” of the virus). This special protein coat is stable even at low temperatures which allows the virus to survive even in frigid temperatures. Once the virus is inhaled, the protein coat gently melts in the throat and releases the virus.
Just because a culture is different does not mean they are “backward”.
Vomact – You might want to check some leading research journals to see how a “backward” country is collaborating with other nations on leading research into the cold and other viral infections. With your “backward” view, seems you’re the pig in this house.
to answer your question DrVomact the actual reason people get the flu more often in the winter is usually because first of all they get very cold outside and 2nd the most important is that they get cramped indoors with many other people allowing viruses to spread more easily, the reason why it is more sever in places like china/beihjing or however you spell it is that there population is Denser so there is a easier path for viruses to travel and infect more people.
People get sick more during the winter due to the natural reduction of Vitamin D due to loss of UV rays during that time.
I have not read the details of the experimental method used by Professor Eccles, but it does not seem very rigorous.
Immersing the feet in ice water would only reduce the temperature of the feet (and perhaps the lower leg), but not the core body temperature. The site of infection is in the throat and sinuses (extending to the chest if severe), but the temperature here is not going to be affected by cold feet. On a cold day however, the chilly air would cool these parts of the body – though how much is significant is unknown – not the feet.
“Cutting off the blood flow reduces the supply of white blood cells which are the immune system’s primary weapon against germs” – this is fundamentally wrong – the blood flow is not “cut off” – it is redirected to the torso – the number of white cells remains unchanged, as does the ability to fight infection.
While it is true that metabolic rate decreases with decreased temperature (just like all chemical reactions) this decline is not significant at the range of body temperatures viable with life – normal body temperature is 37C – hypothermia is set at 35C and very few survive a fall to 32C (except those on bypass having heart surgery)
The fact that transmission of the cold and flu viruses is higher in cold seasons, is thought to be mainly due to the increased crowding of people in buildings and public transport (unwilling to go out). In addition, rather than being “stable even at low temperatures” it is more accurate to say that they are LESS stable at HIGHER temperatures
By decreasing the temperature of any extremity for a period of time you would decrease the core temperature.
While an infection may manifest in a particular area, you will find that the infectious agent is present in other areas of the body. It just happens that the majority of the infection is localized to a particular area.
So you’re saying that a significant diversion of blood flow does not mean “cut off”. I’m fine with that, but a a significant diversion of blood flow directly impacts the population of white blood cells in an area in the body. Semantics.
Perhaps there are multiple factors that can contribute to the increase in flu infections? How does your theory contradict the stated theory? Also, the author cited a study to back up their theory. Please cite yours for evaluation.
Here’s a more comprehensive overview of Eccles’ study. He says “It’s well known that chilling the feet causes vasoconstriction in the nose.”
This wasn’t well known to me; in fact I was impressed by the apparent lack of connection between the temperatures of the feet and the nose, given the evidence he presented. The risk of developing symptoms of a cold more than doubled when peoples’ feet were immersed in ice water, which seems to suggest that there’s a causal relationship at work.
Granted, the p-value of this result is a little large for my tastes at 0.047. (A p-value is the chance that the result would’ve happened even if the tested hypothesis were false. Lower p-values mean an experiment is more convincing.) This p-value is only just below the customary “p < 0.05″ limit for clinical studies, and I tend to agree with researchers who want to place a more stringent limit like “p < 0.01″ in order to prevent the publication of false positives. But I think Eccles’s findings are strong enough to take this hypothesis seriously, at least until more evidence is gathered.
I’m not talking about a decrease in metabolic rate. Instead, I’m proposing that as the body temperature drops below 37° C, metabolic activities are focused on a specialized set of activities that keep the body warm. For example, blood flow to the extremities is restricted by vasoconstriction, which requires energy. When that energy runs out, the blood vessels open up again even if the body is still cold, which results in a feeling of warmth. As a result, it’s common for hypothermia victims to shed their clothes right before dying.
I’m guessing that there are other mechanisms that perform the same trade-off. Energy that would otherwise be sent into the immune system is re-routed to tasks that provide/retain the most body heat for the fewest calories of fuel. I doubt this phenomenon would result in a lowered metabolic rate. Quite the opposite, in fact.
You’re right to say that the influenza coating melts at higher temperatures, which results in an alternative mechanism: “warm weather melts the coating, slowing the infection rate of influenza and other similarly coated pathogens.” This may act in concert with the other hypotheses I’ve discussed; Anonymous is correct to say that multiple factors may account for the cold weather/sickness correlation.
What caught my attention wasn’t the stability of the coating at lower temperatures, but rather the fact that the coating melts gently as it’s warmed. There’s no phase transition that could harm the virus; it’s completely continuous. That seems like a very effective cold-weather adaptation.
I just noticed an inconsistency. The first link to Dr. Eccles’s research says that 29% of the group with chilled feet developed cold symptoms, compared to only 9% of the control group. Each group had 90 people, so that’s 26 and 8 people sick respectively.
But, the second link explicitly says that 13 people with chilled feet got sick compared to 5 of the control subjects.
Both articles agree on the number of people in each group, so there’s a problem here. Which article, if either, is correct?
I emailed Dr. Eccles, and he said that both statements are correct, but they’re referring to different parts of the experiment. The first statement refers to colds diagnosed via symptom severity changes and the second relates to self-diagnosed colds.
He was also kind enough to give me a copy of the paper. The first link’s data (29% chilled colds, 9% control colds) was based on a repeated survey that ranked various symptoms from 0 (not present) to 3 (severe). This result has a p-value of 0.001.
The second link is referring to a simpler repeated question “are you suffering from a cold?” This result has the p-value of 0.047 which I previously quoted.
Something’s been bothering me about Dr. Eccles’s study. It couldn’t possibly have been double-blind because there’s a perceptible difference between ice water and an empty bowl. I wonder if the increased reporting of cold symptoms could have been enhanced by the subjects’ expectations of catching a cold.
I’d like to see another independent study reproducing these results at some point, but the only way to create a truly double-blind study would be to sedate the subjects, immerse their feet, dry them off and warm their feet back up, then wake them up. Hopefully the subjects wouldn’t know if they were in the control or experimental group if these precautions were taken.
Dr. Eccles quickly responded to these concerns:
Cold Weather Really Can Make You Sick is a statement which is backed up by a considerable amount of epidemiological data. Studies have shown very convincingly that there is a very direct correlation between sudden drops in temperature and morbidity and even mortality.
On the topic of the common cold one very important factor that is a likely contributor to the common cold is the drying of the upper airways. Airways are instantly challenged when exposed to cold air, which happens with the first breath you may take on a cold day. Cold air is inherently dry and the inspiration of this dry air was first studied by Dr McFadden who clearly established the penetration of cold air deep into the thoracic region. Prior to Dr McFadden’s research it was commonly believed that all inspired air way preconditioned extrathoracicly. Many health care professionals still believe this.
The result of cold air penetrating deep into the airways is the potential to dry the mucus membranes lining the airways. The mucus membrane is the airways front line of defense. When the airways dry they loss this line of defense and become exposed to any pathogen which may be present in the airways awaiting the opportunity to attack. Of course the body has methods to compensate for this challenge but it cannot compensate immediately and hence just a few breaths of cold air may be enough to trigger that cold or sore throat.
All of this is very consistent with Dr Eccles’s cold feet study since the hypotheses are centered around the occurrence of vasoconstriction and blood shunting to the core. When this occurs the blood flow particularly in the nose is reduced and as a result the airway mucosa may dry and leave the door open to virus and or infection.
Best advice is never doubt your mother.
Heh. Agreed. Thanks for the info!
What about the fact that people in tropical regions tend to get sick during the rainy season?
I’ve previously noted that people stay indoors more in the winter, which increases the chances of spreading germs. The same effect likely happens during the rainy season. It’s important to remember that a combination of factors are responsible.
I don’t know about you, but my nose runs when it gets cold, not dry. It drys out inside where the heat is contained. Where the viruses sit waiting to get picked. Usually by the inanimate items the infected person brought home with them from what ever public place they were.
I have a theory on that. When it gets cold and windy, your eyes tend to create more tears probably so the eyes won’t get too dry. Since the tears are evacuated from the eyes to the nose, this is why you have a runny nose in cold and/or windy weather.
However, I always thought it was false that cold weather can make you sick, and I still have to be convinced. I do not get more sick in the winter than in the summer, and I live in Quebec, where temperature can drop regularly to -30°C. I like the theory about “when it’s colder, you get in more confined spaces with more people, which help the propagation of the virus”.
Another interesting idea about the relationship between the increase in cold and flu incidence during cold weather is that there appears to be an inversely proportional relationship between a person’s vitamin D levels and their likelihood of contracting a viral respiratory illness. Since one of the ways a person can increase his vitamin D stores is exposure to sunlight, it makes sense that with colder weather (and greater coverage of the body) and the less direct sunlight that occur in the winter could lead to lower vitamin D levels and greater chance of illness.
Hmm… my mom also tells me to get outside more. Maybe this is why.
I’m curious to see if this relationship is spurious or not. They say that vitamin D levels are positively correlated with exercise prior to entering the military, and inversely correlated with smoking. Perhaps these factors make vitamin D appear to be related to immunity, when it’s really just a matter of exercising and not smoking. We’ll have to wait until their supplement studies are published to find out.
Anyway, thanks for the interesting link!
I just noticed these sentences in the paper:
So my objections were already considered and disproven.
I live in Los Angeles where it rarely gets below 50 during the cold/ winter season. The amount of energy used to keep my body warm on a 55 degree day in a coat has to be negligible at best, yet I get sick every winter. More so the energy spent has to be significantly less than if I were to jog a mile in 90 degree weather no? And people aren’t getting sick more in summer. And what about athletes in general wouldn’t they have insanely high infection rates? So it can’t simply be the depletion of an energy payload diverted from the immune system can it? The air and airway theories seem to make more sense if it’s cold weather related at all.
Humans shed excess heat by sweating, which results in dehydration but the energy required probably isn’t comparable to shivering and blood vessel contraction in the extremities, etc.
Conscious exercise also consumes energy, but perhaps involuntary shivering has a higher “priority” in the body’s metabolism than exercise unaccompanied by massive doses of stress hormones. In other words, maybe natural selection favors metabolisms that don’t divert crucial immune system energy to exercise unless the creature is in fight-or-flight mode.
No. That’s why I didn’t suggest that all cold-correlated illnesses are due to a single cause. Multiple factors are certainly involved, as discussed here and here and here.
Yes, I’ve already agreed with Bruce that this factor seems significant. What I’m suggesting is that “vasoconstriction in airways leads to a cold” is just one example of a more general pattern where our bodies sacrifice long-term health for immediate warmth.
What experiment was this? This experiment described above doesn’t prove anything. First of all, immersing someones feet in ice water for 20 minutes will not do anything but cause their blood vessels to constrict at their feet – called peripheral vasoconstriction. Next, the experiment states within 5 days, 23% of the experimental group developed cold symptoms. Nowhere in the experiment does it state if either of these groups were exposed to a known virus or bacteria. If both groups for example were exposed to the same virus at the same time for those twenty minutes and then observed over the next 5 days with no external contact, then maybe the experiment could hold some value. But we have no idea what this experimental group did in the 5 days after, who and what they were exposed to, versus the control group.
In summary, I do believe that cold weather can lower host defenses. But hypothermia is very different from going out without your jacket for 30 minutes in the 35 degree weather. Putting feet in ice water for 20 minutes is not considered a form of hypothermia.
Aside from the fact that the word “experiment” in that excerpt links to an article describing this research, you must have missed the discussions I had with one of the authors. Judging by the rest of your comment, you missed every other comment in this article, too.
I apologize but I didn’t read every single comment in this discussion. Just a few. However, from what I read, I still feel the study has some flaws.
I looked up the study and found this.
According to the conclusion:
“Acute chilling of the feet causes the onset of common cold symptoms in around 10% of subjects who are chilled. Further studies are needed to determine the relationship of symptom generation to any respiratory infection.”
However in the results section it states: “The subjects who reported that they developed a cold (n = 18) reported that they suffered from significantly more colds each year (P = 0.007) compared to those subjects who did not develop a cold (n = 162).” I apologize if I am incorrect but I did not see any mention of this is the discussion above. Could it be that the patients that reported these changes were more prone to infection due to factors other than chilling of the feet? Or could these patients just report more symptoms because they generally feel they get more sick than others? This brings up another point.
Symptoms are subjective because they are experienced by the patient. As per the last line of the conclusion, “Further studies are needed to determine the relationship of symptom generation to any respiratory infection.” The study did determine any actual infection, just subjective symptoms.
Dr. Ronald Turner of the University of Virginia states “The researchers didn’t check to see if a virus was ever present. They measured symptoms… They didn’t do any virology, so that study has nothing to do with becoming infected.”
There were two studies done in the late 50′s and 60′s and both concluded that cold weather and infection rates by the cold virus were not related.
I don’t think the points discussed above were brought up prior to this, but if they have, I apologize.
Discussed here.
Dr. Eccles already said this study examines how cold activates latent infections.
That’s the point of having 90 people in each group. Larger sample sizes reduce the chances of the experimental group getting exposed to another infection vector “significantly” more than the control group.
Asking people to stick their feet in frigid water then answer some surveys is probably easier than asking them to stick their feet in frigid water, then sit in solitary confinement for 5 days. Good luck getting that study funded.
As Dr. Eccles noted, “It’s well known that chilling the feet causes vasoconstriction in the nose.” As Bruce noted, vasoconstriction of the upper airways dries them out, removing the first line of defense against airborne pathogens. Of course, all this is on the first page of the paper too.
Not surprising, given that Dr. Eccles’ hypothesis concerns activation of latent sub-critical infections. Here’s the last paragraph in results:
There was no difference in colds incidence between the two test groups at baseline as illustrated in Table 1. However, when looking at both test groups combined, those subjects who believed there were suffering from a cold had a history of more colds each year (median 2.00, range 1–10) compared to those who did not develop a cold (median 3.00, range 2–8, P = 0.007).
This last sentence has me confused. It seems backwards. But their conclusion seems reasonable:
An interesting finding in the present study was that the subjects who reported they developed a cold after the chill or control procedures also reported that they suffered from significantly more colds each year, than the subjects who did not report a cold after the procedures. This finding may indicate that there is a sub population in the general population who are more susceptible to developing common cold symptoms each year and that they may have a ‘common cold constitution’.
The real question is, why would these people be more common in the experimental group rather than the control group? As the paper says:
“The differences between the chilled and control groups could have occurred as a chance finding, as it was expected that some subjects would develop cold symptoms due to natural exposure to common cold viruses. The probability value for the different reporting of colds was just below P = 0.05 (P = 0.047) but the P-value for the difference in total symptom scores was more convincing with P = 0.013, and for the dichotomous analysis was P = 0.001. With two different measures of the incidence of common cold providing significant differences between the two test groups it is unlikely that the results are solely due to chance.”
Already discussed, and I’ve already said that I want to see future research.
Yes, of course. The paper’s third paragraph specifically states that Dr. Eccles’ hypothesis regards the activation of latent, sub-clinical infections.
That’s why the paper’s second paragraph includes references to papers (6-8) which make exactly that point.
Also, the citations list two relevant papers.
“Not surprising, given that Dr. Eccles’ hypothesis concerns activation of latent sub-critical infections…. ”
Virus latency or viral latency is the ability of a pathogenic virus to lie dormant within a cell, denoted as the lysogenic part of the viral life cycle. A latent viral infection is a type of persistent viral infection which is distinguished from a chronic viral infection. Simply a latent virus is a virus that is never totally cleared, is not replicating, and not producing any symptoms of infections. HSV, HPV, & VZV are some examples of latent viruses. However, I have never read any documentation stating latency with viruses that cause the common cold. However, this may exist. If you have any literature, please let me know as I’d be interested in seeing it.
“As Dr. Eccles noted, “It’s well known that chilling the feet causes vasoconstriction in the nose.” As Bruce noted, vasoconstriction of the upper airways dries them out, removing the first line of defense against airborne pathogens. Of course, all this is on the first page of the paper too.”
Drying out upper airways does remove the first line of defense against airborne pathogens. But then viruses that cause the common cold are not part of the normal flora of the upper airways, to my knowledge (Again if you have any info that proves otherwise, I’d love to see it). The re-activation of a latent infection would mean they would have to be there to begin with. So not quite sure what you mean by latent sub-critical infections.
“The real question is, why would these people be more common in the experimental group rather than the control group? …”
Not really sure what you mean by this. The people that admitted to getting symptoms of a cold admitted that they suffered from significantly more colds each year. These individuals were both in the experimental and the control group. It wasn’t that only the experimental group stated they suffered from colds more each year. Couldn’t this just be that the experimental group had more people who are more susceptible to colds than the control group?
So I’m a bit confused to what this study proved other than, according to what you said, vasocontriction and drying up of upper airways due to immersing feet in ice water for 20 minutes.
I’m referring to paragraph 3, sentence 3: Some years later Sir Christopher Andrewes suggested that exposure to a cold environment may trigger the development of a cold but only in people who are carrying the latent cold virus. (Reference: Andrewes C. The Common Cold. New York: Norton; 1965.)
I’m not a professional biologist, so I won’t claim to know whether your definition of “latent” is the only correct use for that word in this context. But perhaps you should ask Dr. Johnson and Dr. Eccles that question?
Again, I’m not a biologist, so these aren’t my words. Paragraph 3, sentence 4: Eccles developed these early observations by proposing a hypothesis that acute cooling of the body surface causes a reflex vasoconstriction in the nose and upper airways, and this vasoconstrictor response may inhibit respiratory defence and cause the onset of common cold symptoms by converting an asymptomatic viral infection (sub-clinical infection) into a symptomatic viral infection (clinical infection). The novel idea in this hypothesis was that when common cold viruses are circulating in the community a proportion of those infected will have sub-clinical infections, and that when any of this sub-group are exposed to chilling of the body surface this could aid conversion of a sub-clinical infection to a clinical infection. This study was aimed at testing this hypothesis, by studying the onset of common cold symptoms after acute chilling of healthy asymptomatic subjects, during the winter, when common cold viruses are circulating in the community. (Reference: Eccles R. Acute cooling of the body surface and the common cold. Rhinol 2002; 40(3): 109–114.)
Table 1 states that the median number of colds per year is the same (2.0) for both groups. In fact, the experimental group’s range only goes up to 8 colds per year, while the control group had at least one person who caught 10 colds per year. If anything, the experimental group was slightly less susceptible to catching cold.
Those are just suggested causal mechanisms. The real point is the observed correlation between exposure to ice water and development of cold symptoms. As I’ve said, I’d like to see more studies with larger sample sizes and better controls to make the P value smaller. But the only two studies I’ve found citing this paper seem to confirm its findings, so for the moment I remain impressed with this study by Dr. Johnson and Dr. Eccles.
A third paper.
Well thanks for clearing up the confusion about median number of colds in both groups. I must have misinterpreted the passage.
As far as the correlation to exposure to ice water and development of cold symptoms, I don’t buy it. But I agree with you that further studies should be done to check for actual infections, not just subjective symptoms as it would take out some of the questionable variables.
Thanks for all the links. Very interesting stuff.
No problem. To be fair, I’m a little confused about one of their median cold statements too. Sorry for being rude earlier.
No worries. I apologize as well. I came off a bit arrogant myself.
Very interesting to read all the comments. I really believe people are more inclined to report “symptoms” if they believe they should feel symptoms. So many people are brought up with the teaching that cold air, wet hair, etc will get people sick that they will expect to feel symptoms after the ice water foot soaking.
Whether or not a double blind study is possible is not the point… since it was NOT accomplished, then SERIOUS validity issues are in this study.
I thought his response to these concerns was reasonable. I’ve already unsuccessfully tried to think of a better experiment setup, and said that I want to see future research. If you’ve seen some relevant peer-reviewed research or have a better experimental setup, then I’d be interested to hear about it.
All the cold weather does is it lowers your immune system. Quoting yourself: “Cutting off the blood flow [by vasoconstriction from cold weather] reduces the supply of white blood cells which are the immune system’s primary weapon against germs” and again, “a significant diversion of blood flow directly impacts the population of white blood cells in an area in the body. Semantics.” In conclusion, cold weather causes lowering of the immune system, increasing chances to catching a virus leading to a cold. Logical.
More support:
“The result of cold air penetrating deep into the airways is the potential to dry the mucus membranes lining the airways. The mucus membrane is the airways front line of defense. When the airways dry they loss this line of defense and become exposed to any pathogen which may be present in the airways awaiting the opportunity to attack…When this occurs the blood flow particularly in the nose is reduced and as a result the airway mucosa may dry and leave the door open to virus and or infection.” To which Dumb Scientist posted on 2009-08-25 at 18:24 “Heh. Agreed.”
The experiment and or controlled study only makes a difference is all 90 people were in the same living conditions. Colds and flu are air born and contact.
Did these all 90 of these subjects not go to work, be exposed to the public, did all wash their hands after touching possible infected surfaces, did anyone touch a surface that others did not touch, were any around people who were already infected, did they wear masks, did any have school aged children that they exposed to, did they all have similar BMI, did they consume a similar diet from the same source, were they of similar age and similar heath to begin with etc….?
Just to many variables here.
With lab rats they all eat the same diet, live in the same environments etc….
With humans that is a bit more difficult to control.
Notice that there were 180 people in the study: 90 people in the experimental group and 90 people in the control group.
That’s why I’ve previously said: That’s the point of having 90 people in each group. Larger sample sizes reduce the chances of the experimental group getting exposed to another infection vector “significantly” more than the control group. Asking people to stick their feet in frigid water then answer some surveys is probably easier than asking them to stick their feet in frigid water, then sit in solitary confinement for 5 days. Good luck getting that study funded.
I’m not a scientist but I absolutely concur with the research findings. I work at home so am not out in the mainstream for long periods during the week exposed to infection. It has been obvious to me for years that if I let my feet and ankles get cold – for instance if I just put slippers not socks on – sure as eggs I will come down with a cold. Given I’m often holed up at home alone it can only be the case that the virus has been dormant and is activated by my body temperature dropping. Interesting to read why.
Hmm… that suggests we should look for seasonal fluctuations in colds among people who work at home alone. Since the usual explanation (people are crowded indoors more during the winter) wouldn’t affect them as much, any seasonal fluctuation would be more likely to be a result of lower temperatures. Good idea!
I have been wondering about this as our weather temperatures just abruptly dropped by an average of about 80 F to 50 F in the tropics. People in large numbers are sick, and sicker than usual for the flu season here. My daughter and I both contracted terrible bronchial symptoms that have taken 10 days to go away.
I was wondering whether there was not a common necessary agent in both thermal regulation of the body and immunity. That sounds very simple, and it is simple, and is considered in the ideas mentioned above like restricted blood flow. But what if there is a very simple basic agent, like Zinc or some exact protein carrier, that is necessary for both thermal regulation and immunity. Imagine you have two competing chemical reactions that need one of the same agents but the solution where the reaction is occuring only has a constant supply of that agent. In a time when both reactions need to occur at a higher rate, one or both suffer.
I guess what always bothers me in these studies is that ‘immunity’ is so general. Surely we can break immunity into smaller pieces that can be studied quantitatively. Surely we can identify some exact pieces of the physical, chemical processes that are causing the flus and colds.
Vitamin D, as mentioned above, may be one such commonly needed substance for both thermal regulation and ‘immunity’. But I live in the tropics and it has been damn sunny for this period of colder than usual weather that has caused more flu, bronchitis, etc. Maybe we all stayed inside as it was colder and our vitamin D dropped. I don’t know. I’d love to hear responses.
I haven’t read any good, solid scientifically-based explanations for it, but there is a certain amount of old-timers’ wisdom (some of which IS based in fact) that swears that our bodies use so much energy keeping themselves warm that they don’t have as much left for fighting off colds. My own first thought was vitamin D – even if it’s still sunny, people are probably outside less and they’re covering more of their skin. I have a couple of friends who have recently been diagnosed with horrifically low vitamin D stores – to the point where it’s seriously messing with their endocrine systems – and both are outside without sunscreen quite a lot. Supposedly many Americans have deficient vitamin D stores, so even though it is a fat soluble vitamin, colder weather for a period of time in the tropics may well drop people’s levels enough to have an impact on their immune systems.
I believe you guys might be looking too deep. Have you considered children and hygiene? During the summer vacation they’re not bunched together sharing germs. School starts and the germs begin to spread in the youngest group and brought home to siblings or their snot flying in the local grocery store. As it gets closer to Summer they have started building up their immune systems. Then another generation comes in and the mutations start all over again on new fresh meat. Studies show that hygiene helps keep germs down, common sense; not to detract from any of the above theories. I also believe that crowding people together added with the cold weather, due to running snot moving those buggers around inside us, don’t help any.
Notice that many of the previous comments (starting with this one address the fact that staying indoors allows germs to spread more easily. Recently, MW proposed comparing seasonal fluctuations in colds among people who work at home alone to people who go to work/school or have families who do.
What temperature does this cold weather have to be? Submersing your feet in chilled water seems a little different then going out in 50F weather without a jacket.
Also aren’t there studies that have shown that dunking yourself in cold water (external stress stimuli) regularly actually increases your immune system very slightly?
I think it has more to do with the moisture content in the air (dryness causes illness because the mucus in our noses is impaired) and lack of vitamin D and maybe even a decrease in physical activity in winter.
If cold weather really causes disease, wouldn’t countries with cooler climates have a higher incidence of disease?
Yes, but both involve lowering the temperature of part of one’s body. Dr. Eccles’s experiment isolates that variable from others that could be responsible, such as lowered humidity.
I don’t know. If you find one, please come back and leave a comment with a link.
Yes, Bruce McCormick mentioned dry air and Betty discussed vitamin D deficiency. I hadn’t thought about lower physical activity, except for the implied proximity to other people. I’m trying to figure out how a few months of lowered physical activity would cause one to experience more colds. Any biologists or medical researchers want to help me out here?
First, neither Dr. Eccles or I am claiming that cold weather causes disease. I’m just reporting on suggestive evidence that cold weather activates latent infections.
Second, this would only be true if everything else were equal. But people in colder climates wear more insulating clothing and sometimes go to great lengths to avoid exposing themselves to cold weather. Also, colder climates are more common at higher latitudes, which also happens to be where most of the world’s richest countries are. Presumably average wealth correlates with the average quality of health care to some extent, which would complicate your proposed experiment.
Just thought I’d point out; in the tropics where I live, the seasonal temperature changes less than 10 degrees F “season” to “season” yet we still get sick in the winter and get flu viruses running around.
I’ve always wondered if, in colder climates, the dry cold air, drying out the nose and throat aren’t more responsible for transmission of some viruses. No/diminished protective mucus, more chance of a pathogen finding fertile purchase. Flu viruses aren’t just endemic to 40 degrees north latitude and up. They hit warm climates as well where no substantial seasonal climate change can be blamed. Are cases of the flu more predominant in NYC than San Diego or Atlanta?
Actually I’ve lived in the tropics before moving to Colorado and I must say it gets about 5 times worse in Colorado than I’ve ever seen in Hawaii. Sometimes at my school there can be up to 4/5ths of the students home because of sickness.
That experiment sucks and that is BAD science….. What if the virus/bacteria was in the water and not on the COLD? Why a empty bowl instead of a bowl with hot water?
I have one question for whoever wants to answer. I am wondering what temperature should I keep my house this winter? I watched a Dr. Phil show and he said that your house should be kept at 64 degrees F to 70 degrees F, especially when you sleep at night. I feel like his statement is incorrect because those temperatures are below room temperature. Also, from reading these postings, it states that the cooler the temperature the more likely your body’s immune system becomes weaker. So what should I set my household thermostat to this winter?
The reason for that is you don’t want it to be too warm 73 or 74 may be good during the day but at night if it’s above 70 and you’re under bed sheets you might (in your sleep of course) throw your bedsheets off you becoming a bit colder and causing you to toss and turn so you won’t let your body get a nice resting sleep to recover, but if it is at 64 degrees your body will react to that and stay still under the snug and warm blanket as you won’t get uncomfortably hot.
Dumb Scientist, this is some really good stuff. I’ve been doing some googling on trying to find out how temperature is affecting our immune systems. I just moved into this apt that has poor air flow system and ventilation. Windows don’t trap any air in or prevent any from coming in.
Anyhow, I’m trying to determine how to prevent my son and myself from constantly feeling sniffly/coughing because we keep activating viruses because the air in the apt constantly gets changed from heat to air to compensate.
Also, I’ve been fixing him green tea/fresh lime/honey often because I believe it will help his immune system tremendously.
Lastly, best line on this whole page “listen to your mother” lol!
I had not had a cold or flu for about five years. All that time I was living in a modern apartment with thermostat controlled heating, I rarely got cold because of that.
Two weeks ago I moved to a bigger home with no thermostats and electric heating. For the first two weeks I have been regularly cold in my extremities, and low and behold I now have a cold.
I take a strong multi vit each day and am generally health conscious, that is why i googled whether the temperature makes one susceptible to colds, as it seemd the obvious conclusion in my circumstance, I wanted to see if any science would back it up and it does seem to make sense after reading these posts.
Merry Christmas and a Happy New Year!
the mind plays a roll in the perception of the state of environment.
will the mind also effect the state of environment?
not that thinking it will make you feel sick, but that the body reacts as if it is sick? physiologic games….
possibly if the study was to sedate the personal, so they never know what context they were used in the study. problem being that they would have known that they were involved in the study,so that there was a chance that they were ‘exposed’…
this could turn into a wonderfully revealing study if compared to a control group that had not been sedated (they consciously knew if they were cold). the effects of perception and how the body reacts.
another option would be to keep the personal sedated for the duration of the five days. just that it does not seem feasible to keep 90-180 people unconscious for that length of time.
It’s germs, bacteria, viruses and mold that makes us sick, not the cold weather. The cold can make you feel uncomfortable, and in extreme cold can cause hypothermia, or possibly lower resistance. I’ve always thought, however, that the colder the temperature gets, the slower the bacteria and mold multiplies …. Any scientists who can comment on this issue … ???
I lived in the Pacific Northwest for 30 years, worked in the cold, rain, wind, snow and ice for many years, but actually was healthier during the cold weather. My grandfather worked hard all his life and even had a garden all winter long, and was never sick all his life!
I now live in California, work in my garden even when the temperature is below freezing in my bare feet, summer shorts and tank-top, and have no problems when I’m outside.
When other people are sick, I’m healthy! I have to laugh when people say it’s cold here …. What about the people who live in the high mountainous regions, and go bare foot their entire life, even in below-freezing weather!
We must consider many factors when examining the causes of sickness, diseases, and physical complications …. Our age, physical condition, diet (huge factor!!!), exercise (or lack of-also huge factor!!!), alcohol, smoking, medications, drugs, pollution, chemicals, work place, genetics, etc.
These factors can work for us or against us …. I’ve noticed over the years (I’ll be 55 soon) that the more healthy I eat the better I feel. The more I exercise the stronger my body is and the more strength I have when I do get sick, and seem to get well quicker, and still get around better even when I am sick. When I slack off and don’t eat right, and don’t get enough exercise, my body is weaker, and I seem to get sick easier, and take longer to get well.
Dear Dumb Scientist,
Thank you for taking the time to answer all these people’s questions (and the many rude arguments) with such grace.
You have helped to enlighten one mom in Canada, who now understands more about immunity. Thank you.
- Canuckian Mommy ;)
Thanks for the info.. When I was in the Philippines which is a tropical area and hygiene is not as clean as other developed countries the temperature dropped to where I thought it was the beginning of fall in the US. Now going from temperatures of 90 degrees and then suddenly it dropped to around 50 because of the wind chill, keep in mind I was just wearing shorts at the time due to the 90 degree weather. It was a bit dramatic drop in temperature but I felt the chills and a couple hours later I had a fever… I make regular trips to the Philippines and noticed during rainy seasons the temperature also drops a bit so just because there’s no winters in the tropics doesn’t necessarily mean the temperatures don’t drop. It just doesn’t get cold enough to snow but it still drops enough for you to feel a chill especially in the high altitude areas. I’m not a scientist at all but I guess it depends on what you as an individual feels that point to were you feel uncomfortable and stressed. For me,If I’m not in heat I’m stressed and I will get sick. I never get sick in the summers, it’s always when the weather drops in temperature and my body is fighting to stay warm do I end up getting sick a few hours later and the whole staying indoors more in the summer and the winter doesn’t work for me because I work the same amount of hours all year around and I barely go out side even during the summer so that theory does not work for me and after reading alot of the comments on here that there are other factors involved makes sense.. but I know for me personally it’s when I feel chills and I can’t get warm right away that is what triggers my cold.
No-one has commented critically on the main alternative hypothesis – that the increased prevalence of colds in winter is caused by people crowding together in buildings. This hypothesis seems very unlikely to me, for the reasons I shall give below. Further, no-one has referred to any experiments to try to confirm or deny the hypothesis. It should not be accepted on faith, without any attempt at experimental confirmation, although I do admit it is hard to think up realistic experiments to test it.
The reason I think the hypothesis is a priori unlikely, is that I think in many places, people live most of their lives indoors (and equally crowded together) whether it is summer or winter. Being indoors can protect you not only from cold but also from heat, wind, rain, fluctuations in temperature (e.g. somewhat warm to somewhat cool) intense sunlight, and so on. Public transport systems e.g. buses, trains are almost always enclosed, and people do not stop using them or even, so far as I can see, use them significantly less, in summer, because they still have to get to work. Even if the climate etc. did make it theoretically possible to move to living and working outside, people are not going to move their offices, hospitals, schools, televisions, beds etc. outside because it would be too time consuming to move everything, and find a place outside to put it all, and then have to move it all back inside again when it got cold or rained.
Yes, maybe people do have a few barbecues outside (though still usually with a number of people close together) and take a few more walks in the park when it is warm, but is much too small an effect to be likely to cut disease transmission much, when you consider how much time people are still spending indoors together. Anyway, if anyone wants to argue the contrary, to have a proper factual argument, the first thing would be to find out by proper studies and surveys how much time people actually are spending indoors and outdoors at different times of the year, otherwise the argument is based on bare assertion.
The argument someone gave earlier about schools being out in summer seems a better one than the general “people go outdoors in summer” argument. However, I still think it is unlikely to be a significant factor. The reason I say this is that where I live (in England) the schools only start their 5-6 week summer vacation in mid July, but in my experience the prevalence of colds has already reduced greatly considerably before then. Colds are known here as elsewhere as mainly a cold weather and especially winter phenomenon, not an autumn through to mid summer one, and despite the fact that schools are still in session, colds from May onwards are not nearly as common as winter colds, in my view, though of course that should be checked for a proper scientific study.
To be fair, MW already mentioned that he works from home alone, so the standard crowding explanation wouldn’t apply to him. In response, I speculated that we could test the crowding hypothesis by studying people who work from home alone, to see if their colds exhibit seasonal fluctuations. I do like your suggestion of correlating the timing of school breaks to the flu season to test Marcus’s hypothesis that children are primarily responsible for spreading colds.
I generally agree with your skepticism of the crowding hypothesis, both for the reasons you listed and because it seems like the effect would be reversed in equatorial regions where people tend to spend more time indoors during the summer to escape the heat, while their mild winters don’t discourage outside activity. So in those countries the crowding effect on incidence of colds would be reversed from that experienced in temperate and polar regions.
As you say, all proposed explanations should be rigorously checked with proper scientific experiments. I’m also a little disillusioned at what seems like a lack of rigorous experiments studying the connection between cold weather and sickness, but I’m not an epidemiologist so I might have simply overlooked the more compelling studies.
Here is some info that will help muddy the water! From Discover Magazine. The first paragraph:
“Everyone knows that winter is flu season, but until now scientists didn’t know why influenza cases spiked during the colder months. They came up with plenty of hypotheses–for example, they proposed that people are more exposed when huddled indoors, and that lower melatonin and vitamin-D levels can weaken immune systems [ScienceNOW Daily News]–but none of the previous suggestions proved correct. Now, however, researchers say they have the answer: The influenza virus thrives in the cold, dry air of winter. “The correlations were surprisingly strong. When absolute humidity is low, influenza virus survival is prolonged and transmission rates go up” [AP], said lead researcher Jeffrey Shaman.”
Maybe, as in most of biology, these questions are multifactorial.
As a veterinarian, we are very much in tune with the changes that occur in horses due to increasing and decreasing lengths of day light. These changes on the pituitary gland and the reproductive cycles are quite profound, initiation of ovarian follicle production, shedding of the haircoat, increase in sperm numbers with increasing length of daylight (spring) to name just a few. I thought this might play a factor in producing a “flu” season, but from the above information, and prior reports of a winter flu season at the equator, I am rethinking that hypothesis. Is anyone aware of this factor being explored?
As a side note to the comments about exercise and immunity, it very well may be a matter of how much and at what level. Moderate exercise may boost immunity, severe exercise may lower it ??
A good friend who was an olympic gold winning runner in the 1960′s reported to me that his immunity seemed normal to him while training, but that he would frequently contract a respiratory infection 3 to 5 days after a maximal exertion. Often that meant a major, world caliber effort. just a single observation.
Folks, I ALWAYS catch a cold when I get chilled. Even if I go out for 20-minute hour walk (not being dressed properly) and don’t touch anything or anyone, I still catch a cold. I know it. I feel it when it happens, and no one on earth can convince me that it is a myth to catch a cold by being chilled. I know cold is caused by a virus but it DOES infect me when I get chilled.
Even if the experiment with the cold feet leaves alot of room for argument, I want to say I know that being cold makes me get sick.
When they did the experiment they should of simply put people in a very cold room or cold area, not use ice on feet!
I think it must be true that parts of our bodies already contain a small amount of cold and flu viruses every day of your life, especially within the ears. I think when our bodies get chilled (beyond the point that we are accustomed too), the defense/immune system begins to stall, and the germs that were being fought off before,suddenly can breach the bodies defenses,and the virus infects . When we get warm our immune system is undoubtedly working better, even if its only because we feel better and more comfortable. I think its been proven already that how we feel mentally can strongly affect our health and immune system. Also I just want to point out that the disease is in fact called a COLD, and has probably been called that for thousands of years, since before we had scientists, or records. It was called that because people knew that everytime somebody got too cold, they got this same disease, which they started calling a COLD. So the cold air doesnt cause the virus to suddenly exist, it exists year round, the cold air simply weakens our bodies immunity to getting infected by it. Do all the studies you want and this fact will still hold true.
p.s. the reason other people can infect us is simply a matter of they have alot more active virus cells to infect and attack us with.While we may always be exposed to these cells everyday, the amount matters. its alot easier to get infected when exposed to several million disease cells then if you were only exposed to say, a million or less of them.
Here is my problem with the the theory that energy is diverted from the immune system to raise body temperature. Why is this energy diversion just in response to temperature? Using this logic, any stressful event should cause a cold. Boss yelled at you today? As far as your body is concerned, someone yelling at you could be trying to kill you. Better divert energy from the immune system to power the muscles and prepare to fight for your life! Going out for a jog later? Your body probably thinks you are running away from a predator. Again, better divert some energy. Based on the energy diversion theory, humans would be sick almost all the time, and those of us who exercise would be the most sick. Now, I realize that prolonged and continual stress, including physical stress, can weaken the immune system. In that sense, continual and prolonged exposure to cold could definitely be stressful to the body. But the key words here are “prolonged” and “continual.” Walking to the mailbox without a jacket would hardly be prolonged and continual.
My niece is a nurse and we have gone back and forth over this so many times. My mother used to say to my sister and now to her grand children to please cover feet in a drafty home and when going outside when it is cold enough to make the body shiver. She will say not to go out in the same weather conditions wet at all, but especially not with wet hair.
Their response is usually something rude in return for the concern and love that was expressed by my mother. Rudeness blended with some brand of false-confident laughter? Not only rude but absurdly disrespectful and mean, insulting, and just wrong in the same measure! I noticed from a veary young age that my sister was very often sick and with horrible, deep, coughs most of the time. My sister lives in bare feet and so did her children in almost a rebellion against my mothers advice to the point of nearly caughing immediately after stating “mother! It doesn’t hurt anything”! The same happens with my niece and with her children.
The same has always happened to me until I learned for my own, over time. Especially when I am forced to breath cold air into my mouth repeatedly from running or working or climbing a hill, unable to breath properly through my nose due to dryness and blockage. There seems to be something very obvious about the simple advice to wrap up and keep extremities, especially your head, covered when exposed to dramatic changes in temperatures from warm to cold, no matter the season. I’ve personally noticed that the same can happen when I am dressed light because of warmer exterior weather and enter very cold, air-conditioned interiors. Sneezing, coughing, congestion, feverish, sore throat. This is always worse in winter, but I take a jacket with me in the car although the exterior temps are in the 90s. My office and many restaurants are very very cold in summer. I completely disagree with the grouping of people, as that has not been a factor in my personal life at all.
I have been very successful about averting colds for several years now, even when I had to contend with minus degree weather interior and exterior for extended periods of time. The only time I’ve ever experienced cold like symptoms and missed work was when I was caught in a situation where I was unprepared to face cold air and did breath deeply into my mouth for several minutes. I always new what was to follow and though symptoms did begin quickly after the event, I have learned that taking a very long, hot shower and going immediately to bed will always nip it.
All of the arguments above that support our mothers advice seem very reasonable, but I do not need science to prove what my life’s tests and controlls and experimentations have already proven time and time again. Proven even by non-believers, and those who would disrespect the advice handed down from ages past. We are too quick to judge common wisdom and too quick to accept anything stamped with the seal of scientific research, which often seems to overlook important conditions of their own tests and promote false positives towards a desired outcome…?
Oh…. And another thing… All of the explanations given above are great, either way, but again, it’s easier to say “don’t catch the cold! Wrap up!”. You may argue that, if a man jumps off of a six story building… Jumping didn’t kill him, falling didn’t kill him, the building didn’t kill him, impacting the earth didn’t kill him… It was a very specific, lengthy autopsy report that will tell you what exactly killVed him… Needless to say that the specifics aren’t that important and generalities are safe to assume when your giving out loving advice that is so well proven throughbtime… I think it is well enough just to say… “Honey, don’t go a-jump’n off no buildings today!” “Don’t fall and break your neck!”. That’s all I have to say about that.
“The same has always happened to me until I learned for my own, over time. Especially when I am forced to breath cold air into my mouth repeatedly from running or working or climbing a hill, unable to breath properly through my nose due to dryness and blockage. There seems to be something very obvious about the simple advice to wrap up and keep extremities, especially your head, covered when exposed to dramatic changes in temperatures from warm to cold, no matter the season. I’ve personally noticed that the same can happen when I am dressed light because of warmer exterior weather and enter very cold, air-conditioned interiors.”
I’ve been reading lots on this because I, too, have a mother who constantly tells me to dress warmly and it is highly annoying. Rudeness works both ways – I constantly tell her that I don’t believe in this old wives tale and tell her to please stop telling me how to dress, but she ignores me. I find this to be rude even if she does “mean well.” Your observations, and this entire old wives tale, that you always catch a cold after being exposed to cold suffers from the fallacy of post hoc ergo propter hoc. This fallacy states that just because B happened after A does not mean that A caused B. Correlation does not equal causation. Now, there is no doubt that colds are correlated with cold weather. So, what might be the actual cause. The reason for this is that winter weather tends to bring lower humidity. This is especially true when you are indoors in a heated environment. Low humidity dries out the mucus membranes in our noses and sinuses, which in turn, makes them less resistant to viruses. This would also explain your observation about walking into an air conditioned room in the summer. Air conditioning not only cools a room but also lowers humidity. You get the same affect. So, it may be true that “bundling up” may help prevent colds if the person “bundles up” to where they cover the nose and mouth with a scarf. A scarf or some other covering will help prevent the nose and sinuses from drying out due to the low humidity, thus making them more resilient to viruses. However, just wearing a warm jacket probably won’t help. You’re better off drinking more water (another thing people don’t do in winter because they don’t sweat as much) than wearing a jacket.
Your argument about jumping of a building is silly. In that example, we see a clear chain of causation: you jump off a building, gravity causes your body to accelerate, you impact that ground at a high speed, which causes major trauma and death.
With the cold weather causes colds theory, we are missing a huge link in the chain of causation. What is it about cold weather that causes illness? No one has explained this. I don’t care how many people claim that dressing warmly has prevented them from getting sick – anecdotal evidence is not enough to establish causation.
This information is new: The changing of seasons or temperatures affects the migration of birds which can carry viruses.
An opinion about the common flue and cold can be that the body in either environmental extremity causes a stress reaction in our body. The increased cortisol levels in the moment of stress is interesting factor in the pathophysiology which should be more closely investigated by the professions of interest.
Being cold doesn’t make you sick. If the body’s immune system is weakened by being cold – you’re STILL being sickened by a virus, not from being cold. I’m sure your mother wasn’t referring to a weakened immune system.
It’s still good pragmatic advice if being cold weakens the immune system, as the evidence above suggests. And I’m not just saying that because it’s Mother’s Day.