>The decrease in average body temperature in the United States could be explained by a reduction in metabolic rate, or the amount of energy being used. The authors hypothesize that this reduction may be due to a population-wide decline in inflammation
Let's not ignore the elephant in the room. A sedentary lifestyle with minimal exercise has become the norm.
Which is a relatively recent thing. How does that explain the trend going back as far as the article calls out?
Without facts to back it, you’re projecting an emotional bias. Either anon commenter is a self loathing obese person or pointlessly finds obese people disgusting. Either way you’ve shown your opinions aren’t worth much
Constant inflammation seems bad though? Isn't that one of the hypothesized downsides of too little fibre -> gut bacteria mildly but chronically attack instestinal wall?
Hmm.. I find it hard to reconcile with the fact that obesity is so widespread I the US. Isn’t obesity linked to inflammation through (at least partially) insulin, which is quite inflammatory? Don’t have medical education, so maybe somebody could chime in.
This study is comparing now to the early 1900s, when Aspirin was just starting to take off. Selection bias probably plays a very large part; they may have been able to measure temperatures but I doubt they were rigorous about taking representative cross-sections in 1910. Additionally the bias towards obesity has roughly switched- wealthier people were more likely to be obese in the 1900s, and now poorer people are more likely to be obese.
Given that the people involved are in their 20s I would guess that obesity plays less of a role than you'd expect.
That seems pretty straight forward to measure, you just take the temperature of people who exercise regularly (say three times a week) and compare that to people who work physically demanding jobs, and to people who work in office jobs, and don't exercise.
(I would almost expect, that the study authors know of something like that, and would have mentioned it, if it were the case.)
There is no body temperature measurements in Apple Health from the Apple Watch, but that would definitely be an interesting data point were it available.
Yes, but also a potential privacy concern since if you have temperature data for a female, you could use it to pinpoint when ovulation may be occurring. I can only imagine that due to some of the recent privacy issues with cycle tracker apps that information might already be exploited for some nefarious advertising campaign.
While we don't consider that sedentary, compared to the physical nature of the majority of jobs and lives these people would still be considered sedentary. I think a better comparison would be people who are doing long distance through hikes since their time under tension is extensive and the large distances they travel each while under load would be more respective of per-industrial lifestyles.
Body temperature tends to decrease because of a deficiency in thyroid hormone also. Many of the synthetic chemicals used to treat modern day home goods seem to impact this system. I'd be curious whether there is any correlation there.
The thymus is not the thyroid gland, if that's the connection you're trying to make. AFAIK the thyroid gland is not deliberately consumed unless as medicine.
If anything I've heard the correlation goes the other way. Regular exercise reduces inflammation markers across the board. Some people suggest it even helps alleviate allergy symptoms all else being equal.
I've exercised my entire life, regularly at a high level, and my allergy to cats developed when I was 10 and has only gotten progressively worse over the years. Started with just itchy eyes and skin and is now into full blown allergy induced asthma. I tell almost immediately when I'm in a house that has had a cat in the last few years. It's terrible. One data point and all...
Most people can build up a tolerance. I grew up with cats close to home and never noticed any allergy as a kid. When I got my own indoor cat though, I noticed itching and then flu-like symptoms that got progressively worse. Allergy medication completely relieved all symptoms, and rather than get rid of fluffy I took allergy meds daily for about 2 weeks, then every second ord third day for another month. Now I'm pretty much free of symptoms, but I occasionally pop a pill if the roof my mouth or hands start to itch for any reason.
I dated a girl for a while who owned a cat. I built up a tolerance to her cat (because she'd have the dander on her clothes), but it didn't help with any other cats. I was also still allergic to her cat, but it was at the point where a claritin would help. Mostly it's within half an hour I can barely breath, so it's hard to build up any sort of tolerance, even with allergy meds. Now it's easier for me to avoid cats entirely.
Yeah I tried to be careful with the "some people suggest" because it's still kind of a rumor. I have an eczema problem that tends to get worse when I'm not exercising regularly and gets better when I am. But obviously all bodies are different.
Another data point of one: all my allergies correlate with the amount of detergent/soap/shampoo/deodorant I am using and to whether I've been the past few weeks in the big city or in the rural countryside.
The time period being compared to the present is the very early 1900s, shortly after the invention of aspirin. Air pollution and toxic materials were also much more common.
Typo, I meant the very early 1900s not the very early 1990s. Aspirin was prescription only until 1915.
The story of willowfine is roughly as well known as penicillin. The point is that in 1910-1920 people didn't carry NSAIDs in their purse and pop 400 mg when they felt a headache coming on or their back hurt. That's a big difference.
It's also worth noting that right at that point, the supply of aspirin was very limited due to phenol shortages caused by the war.
Aspirin is an anti-inflammatory; it decreases inflammation. The hypothesis here is that the widespread use of it has caused decreased body temperatures through decreased levels of inflammation.
Nothing in this thread should affect your personal decisions, except the things about obesity and being sedentary. Don't do those things.
Human body temperature varies naturally by about 5 degrees F. This study is talking about a .4 degree change. At the very least, your body can definitely handle it. This is purely an interesting phenomenon that may not even be real.
Aspirin is very well-studied and definitely known to be very beneficial for your lifespan and quality of life. You should absolutely not throw away all that knowledge because it may be tangentially related to arbitrary theorizing (about inflammation) on a strange result on sketchy data from uncontrolled groups with unknowable biases. Medicine is proven to be good for you. Even if it does have unknown negative effects -even if this is an effect that we don't know about, that may not even be bad- you should not disregard medical wisdom for the sake of what you don't know.
If you're talking about a daily dose, it is really something a doctor should be aware of and give a stamp of approval. It's a blood thinner, which means if you have any other anticoagulant med or issues it can be dangerous.
Relatively speaking, it also has a fair low LD50. For a person around 150lb, 40 standard 325mg pills can be fatal. In fact you'll almost never, outside of hospital supply, find the 81mg chewable version in quantities higher than 36 in case children get a hold and think they're candy. Even then, a 2 year old downing a whole bottle would still be close to an LD50.
All in all, despite being extremely common and cheap to the point of nearly free ($10 for a year's daily supply) it is actually less safe than other NSAID class drugs. But then none of this stuff, strictly speaking, is "safe" if it is used outside of it's normal use parameters.
You should not be taking aspirin for headaches and such. It has worse side-effects than alternatives (thinning the blood, hard on stomach lining, children should not take it, can cause Reye's syndrome, etc).
Yes, but widespread use didn't immediately follow. Supply problems (which might have been deliberate through competitors) extended through the 1915 time frame. Even then, casual use for everyday aches and pains would have been reserved for the relatively well off.
Could this also possibly do to an increasing rate of global temperatures? One would think we would simply evolve towards a lower body temp in order to survive in a warm world.
You're being downvoted but I can certainly see why someone might make this mental leap. Instead of downvoting you and driving along without comment let's think about this.
CO2 levels for example can negatively impact cognitive function [1], perhaps this could have some impact on energy expenditure in the brain which might reduce body temperature some. Bodies will absolutely adjust to temperature changes as well (to some extent). Plausible but probably not a large percentage of a body temperature.
I could see people being exposed to higher CO2 levels though due to the fact there are more and more indoor jobs, and less due to climate change. Even with HVAC systems, a quick Google query makes it seem that CO2 levels are generally higher in offices than outside [2] [3] [4] [5].
And while we're on that brain line of thinking... perhaps the increased consumption of television and mindless scrolling of social media feeds also results in far lower cognitive engagement which also decreases energy expenditure shrugs. Also worth looking at I suspect.
For me I immediately thought of the thermic effect of food. Legumes, many spices, nuts, seeds etc all tend to have higher thermic effects. Perhaps eating a highly refined carbohydrate diet has caused a lowering in body temerapture by having lower thermic effects (I don't know, this was just my first mental leap). I suspect there is something here but probably not a major percentage of the difference.
Since 1900 CO2 has gone from 300 ppm to 420 ppm. That study looks at 900+ ppm CO2. They also controlled that by doubling the ventilation speed of the room, which would definitely have had secondary effects.
More importantly, you can't infer anything about the CO2 levels when they were being measured from the global CO2. Big buildings would have had very high CO2 levels since there's no central air. Small buildings would have much lower CO2 than any current buildings when the windows were open, and much higher otherwise. Oil or gas lamps would raise the CO2 levels a ton. Proximity to coal furnaces would have had a huge impact. Fireplaces too.
Bottom line: global CO2 levels have virtually nothing to do with how much CO2 people are exposed to.
As an adult, my body temp has always been low, around 97.2*. I also never get fevers. I'm also very athletic- I bike 3-4 times a week. Maybe there is a correlation with sedentary life, but I don't think it's a factor in my case nor many others.
People who exercise have lower temperatures during sleep, similar or higher temperatures otherwise, and the same maximum temperature, which occurs during the evening.
I’d say the bigger elephant in the room is that thermometers have moved from an accurate standard (Mercury glass thermometers) to a hodge podge of alternatives.
Some of these alternatives, like temporal scan thermometers vary dramatically.
> A sedentary lifestyle with minimal exercise has become the norm.
The people being studied were in their 20s- obesity has increased 4-5x among children since 1980, but it's still only 20-25% for people in their 20s. Since then we've gotten gym class and advil- they had barely gotten aspirin.
Selection bias probably plays a very large part. They may have been able to measure temperatures but I doubt they were rigorous about taking representative cross-sections in 1910. Additionally the bias towards obesity has roughly switched- wealthier people were more likely to be obese in the 1900s, and now poorer people are more likely to be obese.
That said, muscle mass correlates almost directly with energy consumption. Muscles literally require energy to stay limp. Rigor mortis is caused by the supply of energy being cut off. The majority of the body's energy requirement is spent just keeping your muscles in working order- not even moving.
My first reaction was to agree. However, if exercise ultimately makes the body more efficient, wouldn't that drop your body temp as your heart is beating less.
That aside, the brain burns a significant percentage of calories burned. Perhaps on whole we are thinking less?
People who exercise have lower temperatures during sleep, similar or higher temperatures otherwise, and the same maximum temperature, which occurs during the evening.
So it's a wash then. Correct? Which leaves the possibility of less it being a brain issue. Lower temps means less calories burned. There are many ways to accomplish that.
Whatever happen to HN being a space where a legit "what if?" was explored, not knocked?
It's almost certainly not a wash, unless all of the people in the records are having their temperatures taken while they sleep. People who are physically fit will tend to have very slightly higher body temperatures (less than what was found in the OP) when measured.
Isn't the real elephant in the room obesity? And a culture around lifestyle and low-quality food that actively promotes it?
If you're sitting on your ass all day and then going out to drink a gallon of HFCS-infused coke (free refills) and a low-budget meal that could satisfy a starving family, of course you're gonna get to this point.
My personal thought with the US is "why does everything have to be so big?"
> Let's not ignore the elephant in the room. A sedentary lifestyle with minimal exercise has become the norm.
Huh? fitness industry is booming! Gym attendance is near all time highs! More and more people are eating healthier and switch to healthier and more active lifestyle.
Assuming this wasn’t satirical, but it’s hard to tell sometimes.
The rates of intentional exercise - going to a gym and working out - are certainly on the rise, but the actual rate of exercise is more lower than it was a hundred years ago. The job market has switched in large part to sedentary jobs from active jobs. And diets are much less healthy today than they were then because the only diets available (to anyone other than the rich) were relatively healthy. It’s hard to become overweight without the presence of junk food. Not impossible, certainly, but hard.
Sure I guess people in the 1800's who worked on farms were far less sedentary but my parents, and my grandparents and my great grandparents all worked jobs fairly similar to mine and drove to work. And none of them went to the gym like my generation (born in the 80's).
I think that by the time we get to great grandparents, they did get more exercise. Sure, they might have been able to afford a single car, but lots of living had more activity. Housework, for example, took way more work while our great grandparents were young adults and children. Cars themselves were harder to drive with no power steering or brakes (and the early power-assists were very poor by today's standards). Office jobs had a lot more 'work' by their very nature simply because everything was on paper - there is a lot of little back and forth walking, bending, and lifting there. As children, they would have played outside lots and helped around the house (since house chores were more work).
I think there were a lot of these little things that mean that yes, our 'sedentary' grandparents and great-grandparents were a lot more active just because of how life was.
So the summary is they aren't certain why, but it seems like it's due to people being a lot more sedentary, having lower metabolisms and being in climate controlled buildings a lot more.
Unfortunately, it seems pretty predictable given the changes in our lifestyles...
Why is it unfortunate? The article didn't seem to say whether this change was good or bad, although I would assume a decrease in inflammation would be good?
> Economic development, improved standards of living and sanitation, decreased chronic infections from war injuries, improved dental hygiene, the waning of tuberculosis and malaria infections, and the dawn of the antibiotic age together are likely to have decreased chronic inflammation since the 19th century. For example, in the mid-19th century, 2–3% of the population would have been living with active tuberculosis (Tiemersma et al., 2011). This figure is consistent with the UAVCW Surgeons' Certificates that reported 737 cases of active tuberculosis among 23,757 subjects (3.1%). That UAVCW veterans who reported either current tuberculosis or pneumonia had a higher temperature (0.19°C and 0.03°C respectively) than those without infectious conditions supports this theory.
I would assume that less tuberculosis is a good thing (though, this being Hacker News, someone will probably show up to question that assumption too).
Inflammation is one of the body's natural defense mechanisms to issues like infection, or injury. Treating inflammation like it is the "bad thing", while ignoring (or not understanding) the underlying cause of it is not good, and potentially hazardous. People do this all the time by taking ibuprofen to treat headaches or minor pains that are natural indicators that something is wrong (dehydration, infection, etc).
Tuberculosis is a disease, and widely accepted as detrimental to human health. I agree, less tuberculosis = a good thing.
This being a medically related post, more information, and less assumptions is better for everyone. Thank you for adding context.
If anything it would be more desirable for body temp to increase. Makes it harder for Viruses and pathogens to hurt us. Maybe that’s why people are getting sick more often it seems.
Uh, you know people who live in the northern part of the United States experience temps that are on average 10-20 degrees cooler than the southern part of the United States? If what you said were true we would notice a latitudinal difference in body temps. But we don't. In fact many parts of the U.S. have cooled on average in the past couple decades.
It's false[1]; everywhere in the US is 2-4 F warmer than it was prior to 2000. He may have this impression from looking at 2002, which was a particularly warm year. Some parts of the midwest have been cooler than they were in 2002.
The general thing about the person he was responding to being totally wrong was obviously correct.
From your link the baseline average is from "relative to 1951-1980 average". Which was the coldest period of the 20th century. It got so cold in the 70s they were predicting an incoming ice age. It's very dishonest and very wrong to cherry pick the coldest modern period of temperature and then say we have increased by 0.8C from there. Climate is cyclical and there are many Multi-decadal Oscillations in oceans that impact global temperature, rainfall patterns, and overall climate conditions. The AMO, the PDO, not to mention ENSO.
As far as anamolies go, which area is experiencing "cooler than average" (which, as mentioned above, is difficult to do) depends on the year, but here's a map from NOAA showing 2013 temps and clearly shows the Western U.S. experiencing below average temps (from a 1980-2010 baseline): https://www.ncdc.noaa.gov/sotc/service/global/map-blended-mn...
And to underscore the situation in the 1970s I'm going to link to a documentary that starred Leonard Nemoy as narrator in 1978. Quotes below and link below to clips from:
“In Search of…The Coming Ice Age”, narrated by Leonard Nimoy (Spock from Star Trek):
“…sea coasts long free of summer ice, are now blocked year round…”
“…the data shows temperatures in the arctic have fallen dramatically over the last 30 years…”
“…in most locations the drop has been about 2 degrees Centigrade…”
GISS also claims to have global temperature data from 1884 that doesn't exist. They interpolate and make up numbers when they go back that far, as we don't have records from much of Asia, Africa, eastern Europe and south America during that time, even huge swaths of Australia were not covered by temperature gauges. We didn't really start getting quality global temperature data until the satellite era.
> From your link the baseline [...] by 0.8C from there.
You goober, I was comparing the measurements from 2000 onward. You specifically said the past couple decades. The reference point does not matter at all.
> As far as anamolies go, which area is experiencing "cooler than average" (which, as mentioned above, is difficult to do) depends on the year, but here's a map from NOAA showing 2013 temps and clearly shows the Western U.S. experiencing below average temps (from a 1980-2010 baseline)
You just complained about cherry picking and now you're looking at a single year that was slightly colder. On average, the US is warmer everywhere.
> GISS also claims to have global temperature data from 1884 that doesn't exist. They interpolate and make up numbers when they go back that far, as we don't have records from much of Asia, Africa, eastern Europe and south America during that time, even huge swaths of Australia were not covered by temperature gauges.
Still irrelevant to the last couple decades. Sue me for trusting NASA though, I guess?
I think GISS is not trustworthy. Honestly, they engage in data tampering and manipulation and they're not honest about historical climate data and it's limitations (prior to satellite era). The margin of error for data prior to satellite era is higher than the observed warming in the 20th century.
UAH is a good resource (University of Alabama-Huntsville in conjunction with NASA, albeit a different department than GISS) and they show a 0.13C per decade trend since the 80s. That being said, because global temps are not evenly distributed, some areas are experiencing cooler temps and some areas are experiencing warmer temps. Averages hide a lot of nuance. See below for latest chart from UAH:
Fuck off. Roy Spencer is an Evangelical creationist who wrote a book about evolution being wrong. He believes humans have no affect on global warming and that more CO2 in the atmosphere is a good thing:
The University of Alabama-Huntsville satellite temperature record is one of the highest quality measurements of global temperature. It works by measuring the vibration of oxygen molecules around the globe. Since oxygen is evenly distributed at sea level (at ~20% of the atmosphere), it's a damn good measurement. It's a co-designed project that has operational since 1979. Dr. John Christy is also involved in the project. Fuck off with Skeptical Science. It's a smear campaign run by a guy with a quarter of the credentials of Christy and Spencer, who worked with NASA to produce the first ever global satellite temperature recording. They invented the process for goodness sake. Anyone can write a blog. Show me John Cook's groundbreaking achievements. Better yet, argue from an empirical standpoint about the methodology UAH uses instead of spouting off copy-pasta ad hominem attacks. And quit judging people based on their religion. Isaac Newton was a creationist for God's sake. Get over yourself.
Also, here's more research for you to chew on:
The Key Role of Atlantic Multidecadal Oscillation in Minimum Temperature Over North America During Global Warming Slowdown
Shows minimum temps dropping during the last couple decades in North America:
It isn't necessarily a bad link of thinking though with this.
Higher CO2 levels can reduce cognitive function [1]. Reduced cognitive function could mean reduced energy expenditure (a common figure is the brain is responsible for 20% of your energy demands), it may not though. I can see this as being a valid mental leap worth investigating.
I suspect however in this case it's a combination of the things the article suggests as well as the thermic effect of food. A reduction in the amounts of nuts/seeds/spices/whole plant foods consumed, combined with highly processed foods that require less work to digest (a piece of fruit vs a bunch of table sugar), likely means diets with a lower thermic effect from the foods. Lower thermic effect means less caloric expenditure, less caloric expenditure should mean a lower body temperature.
i'd guess that given the antibiotics, better nutrition, wide availability of warm clothes/shoes, etc. natural selection pressure for higher temperature has naturally decreased (in such historically short period that decrease mostly manifested itself in much lower child mortality).
People also became bigger during the last century which results in better thermodynamics, ie. surface/volume ratio, thus less need for burning of the internal fuel, i.e metabolic rate can be lower. Compare - elephant's 96.6 vs. cat's 101.5 body temp.
> As part of the study, the authors investigated the possibility that the decrease could simply reflect improvements in thermometer technology; thermometers used today are far more accurate than those used two centuries ago. “In the 19thcentury, thermometry was just beginning,” Parsonnet said.
> To assess whether temperatures truly decreased, the researchers checked for body temperature trends within each dataset; for each historical group, they expected that measurements would be taken with similar thermometers. Within the veterans dataset, they observed a similar decrease for each decade, consistent with observations made using the combined data.
I'm unconvinced by their method to assess whether temperatures truly decreased. Why wouldn't a methodological error not also apply to the veterans dataset? E.g. all thermometers of an era reading slightly hot (rather than them all being less accurate in any direction)
Yeah, fair point! I'm not well versed in this kind of stuff. So I'm not sure.
Maybe the original paper discusses the point though? Perhaps they have a way to normalize temperatures to a baseline across all data sets and evaluate that way.
Interesting. 100F is supposed to be normal human body temperature, by definition. (Fahrenheit set 100F as normal human body temperature and 0 as the coldest temperature he could achieve, using a mixture of ice, water, and ammonium chloride.) For years I'd heard that the reason normal body temperature is 98.6 is because Fahrenheit was running a slight fever at the time he made his scale, but this article suggests that it might've been accurate, but body temperature has been decreasing. If you extrapolate the numbers in the article out (a drop of just over a degree since the 1800s) to when Fahrenheit made his scale in 1724, it's possible that normal body temperature actually was very close to 100F then.
Thermometers weren't very accurate initially, and the scales were defined multiple times in the early years. Here's what Wikipedia has on this:
According to a letter Fahrenheit wrote to his friend Herman Boerhaave,[10] his scale was built on the work of Ole Rømer, whom he had met earlier. In Rømer's scale, brine freezes at zero, water freezes and melts at 7.5 degrees, body temperature is 22.5, and water boils at 60 degrees. Fahrenheit multiplied each value by four in order to eliminate fractions and make the scale more fine-grained. He then re-calibrated his scale using the melting point of ice and normal human body temperature (which were at 30 and 90 degrees); he adjusted the scale so that the melting point of ice would be 32 degrees and body temperature 96 degrees, so that 64 intervals would separate the two, allowing him to mark degree lines on his instruments by simply bisecting the interval six times (since 64 is 2 to the sixth power).
Fahrenheit soon after observed that water boils at about 212 degrees using this scale. The use of the freezing and boiling points of water as thermometer fixed reference points became popular following the work of Anders Celsius and these fixed points were adopted by a committee of the Royal Society led by Henry Cavendish in 1776. Under this system, the Fahrenheit scale is redefined slightly so that the freezing point of water is exactly 32 °F, and the boiling point is exactly 212 °F or 180 degrees higher. It is for this reason that normal human body temperature is approximately 98.2° (sic) on the revised scale (whereas it was 90° on Fahrenheit's multiplication of Rømer, and 96° on his original scale).
Much more here, with references. An early version of the scale set 96F to human body temperature, apparently because 96 divides evenly in half five times, so it's easy to make graduated markings between the reference points on your mercury thermometer.
I would love to see some research that attempts to correlate this to other species that have local declines in birth rate. Maybe it’s a mammalian response to over population.
No, that's silly. Unless mammals are magic, the only way a species could possibly know about population is by the number of individuals it sees locally, and the number they see. That would cause there to be a huge and noticeable difference between eg rural and urban populations.
I found this passage interesting (about the impact of climate controlled environments on resting metabolic rate)
> Changes in ambient temperature may also explain some of the observed change in body temperature over time. Maintaining constant body temperature despite fluctuations in ambient temperature consumes up to 50–70% of daily energy intake (Levine, 2007).
> Resting metabolic rate (RMR), for which body temperature is a crude proxy, increases when the ambient temperature decreases below or rises above the thermoneutral zone, that is the temperature of the environment at which humans can maintain normal temperature with minimum energy expenditure (Erikson et al., 1956).
> ... Thus, the amount of time the population has spent at thermoneutral zones has markedly increased, potentially causing a decrease in RMR, and, by analogy, body temperature.
I wonder if they simply looked at the antibiotic use. For example when that was introduced specifically, and more so when we started "over-prescribing" it. That's got to have had an effect of persistent low grade fevers that exist in just about everyone.
Body temperatures are currently lower, so the opposite of what you're suggesting with low grade fevers from overprescription of antibiotics.
However, fevers are caused by a subset of the interleukin family, which as a whole causes inflammation. Inflammation was the author's suggestion.
Also, low grade fevers aren't a thing. Fever is caused by the immune system. You can only have a continuous infection with diseases that avoid or supress the immune system. There are a small number of brain-affecting infectious diseases like meningitis that can raise body temperature on their own. Chronically recurring stuff will also give you intermittent fevers, but there's no low-grade. You have it or you don't.
Protsiv, M., Ley, C., Lankester, J., Hastie, T., & Parsonnet, J. (2020). Decreasing human body temperature in the United States since the industrial revolution. eLife, 9, e49555.
The latest temperature data was measured from patients visiting hospital. Older people are naturally more prone to health problems and would therefore be visiting hospital more than younger people, on average.
Our average lifespan is longer than it used to be. I'd assume older people have a lower base temperature. This would skew the results statistically.
In my experience, studies are typically not well constructed.
See the numerous studies that cannot be replicated, the below-the-surface iceberg of unpublished (unfavorable) studies paid for by for-profit institutions, or the shockingly small sample set or biased sample set in most studies. Most studies expose this information implicitly but it's up to the reader to determine the bias or replicate the study.
I was always confused how 37 C was a normal temperature in the US. In the USSR where I grew it was a fever and the normal was 36.6. Could it be the way it's measured?
Temperatures of 37 C and 36.6 C are barely distinguishable with an ordinary thermometer, and both are within the normal range of human body temperatures (37.32-38.76 C).
Not sure about any US/USSR differences, but there can be pretty big differences between people individually, between measurements in the same person throughout the day (or month for women), and between how it's measured. 37°C is an average.
Axillary (armpit) measurements, for example, are a lot colder than oral or rectal measurements. Perhaps the Russians favoured the former, while the Americans preferred the latter?
I suspect there's a nice little bell curve with 37°C in the middle.
Yes, Russia measures temperature in the armpit. Is it really that much colder than in the mouth?
Edit:
A 37 temperature would automatically give you an excuse from school when I was a kid and, obviously, children always were finding ways to cheat. If just putting the thermometer in your mouth worked then either I was in the dark or nobody has discovered this.
When working in offices, I have noticed that people who drink pop/soda daily prefer lower room temperature than people not consuming them at all. I might have "noticed" it because of a bunch of biases, but I'd love to see a proper study on that.
The study was on measurements taken in the early 1900s, not 1800s. Also, it's not like technology suddenly started in the 30s or something. Liquid nitrogen was first produced in 1883. The periodic table was published in 1869. Cells were discovered in 1665. Science was a lot more than banging rocks together.
You would expect the opposite of what you're suggesting, if anything. If water was used for calibrating temperature then there would be fewer good ways to control the impurity level, which would lower its freezing point. Not to mention Fahrenheit originally defined body temperature as 96 F, and it was later corrected higher.
All of the above is totally moot because we have plenty of medical thermometers from the 1900s and earlier, and they are remarkably accurate and the error is not particularly biased in either way. This is a highly researched area because the accuracy of whether thermometers is important to historical and climate research. Medical thermometers from the 1800s are good to at least 1/5th of a degree and instrumentation thermometers were good to hundredths.
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[ 2.3 ms ] story [ 169 ms ] threadLet's not ignore the elephant in the room. A sedentary lifestyle with minimal exercise has become the norm.
Without facts to back it, you’re projecting an emotional bias. Either anon commenter is a self loathing obese person or pointlessly finds obese people disgusting. Either way you’ve shown your opinions aren’t worth much
Given that the people involved are in their 20s I would guess that obesity plays less of a role than you'd expect.
[1]: https://en.wikipedia.org/wiki/Obesity_in_the_United_States#/...
(I would almost expect, that the study authors know of something like that, and would have mentioned it, if it were the case.)
The story of willowfine is roughly as well known as penicillin. The point is that in 1910-1920 people didn't carry NSAIDs in their purse and pop 400 mg when they felt a headache coming on or their back hurt. That's a big difference.
It's also worth noting that right at that point, the supply of aspirin was very limited due to phenol shortages caused by the war.
Human body temperature varies naturally by about 5 degrees F. This study is talking about a .4 degree change. At the very least, your body can definitely handle it. This is purely an interesting phenomenon that may not even be real.
Aspirin is very well-studied and definitely known to be very beneficial for your lifespan and quality of life. You should absolutely not throw away all that knowledge because it may be tangentially related to arbitrary theorizing (about inflammation) on a strange result on sketchy data from uncontrolled groups with unknowable biases. Medicine is proven to be good for you. Even if it does have unknown negative effects -even if this is an effect that we don't know about, that may not even be bad- you should not disregard medical wisdom for the sake of what you don't know.
Relatively speaking, it also has a fair low LD50. For a person around 150lb, 40 standard 325mg pills can be fatal. In fact you'll almost never, outside of hospital supply, find the 81mg chewable version in quantities higher than 36 in case children get a hold and think they're candy. Even then, a 2 year old downing a whole bottle would still be close to an LD50.
All in all, despite being extremely common and cheap to the point of nearly free ($10 for a year's daily supply) it is actually less safe than other NSAID class drugs. But then none of this stuff, strictly speaking, is "safe" if it is used outside of it's normal use parameters.
CO2 levels for example can negatively impact cognitive function [1], perhaps this could have some impact on energy expenditure in the brain which might reduce body temperature some. Bodies will absolutely adjust to temperature changes as well (to some extent). Plausible but probably not a large percentage of a body temperature.
I could see people being exposed to higher CO2 levels though due to the fact there are more and more indoor jobs, and less due to climate change. Even with HVAC systems, a quick Google query makes it seem that CO2 levels are generally higher in offices than outside [2] [3] [4] [5].
And while we're on that brain line of thinking... perhaps the increased consumption of television and mindless scrolling of social media feeds also results in far lower cognitive engagement which also decreases energy expenditure shrugs. Also worth looking at I suspect.
For me I immediately thought of the thermic effect of food. Legumes, many spices, nuts, seeds etc all tend to have higher thermic effects. Perhaps eating a highly refined carbohydrate diet has caused a lowering in body temerapture by having lower thermic effects (I don't know, this was just my first mental leap). I suspect there is something here but probably not a major percentage of the difference.
[1] = https://ehp.niehs.nih.gov/doi/10.1289/ehp.1510037
[2] - https://www.businessinsider.com/office-air-co2-levels-making...
[3] - https://www.ncbi.nlm.nih.gov/pubmed/26273786
[4] - https://www.planteriagroup.com/blog/co2-levels-in-offices-ar...
[5] - https://www.washingtonpost.com/news/energy-environment/wp/20...
More importantly, you can't infer anything about the CO2 levels when they were being measured from the global CO2. Big buildings would have had very high CO2 levels since there's no central air. Small buildings would have much lower CO2 than any current buildings when the windows were open, and much higher otherwise. Oil or gas lamps would raise the CO2 levels a ton. Proximity to coal furnaces would have had a huge impact. Fireplaces too.
Bottom line: global CO2 levels have virtually nothing to do with how much CO2 people are exposed to.
http://www.altmedrev.com/archive/publications/11/4/278.pdf
Some of these alternatives, like temporal scan thermometers vary dramatically.
The people being studied were in their 20s- obesity has increased 4-5x among children since 1980, but it's still only 20-25% for people in their 20s. Since then we've gotten gym class and advil- they had barely gotten aspirin.
Selection bias probably plays a very large part. They may have been able to measure temperatures but I doubt they were rigorous about taking representative cross-sections in 1910. Additionally the bias towards obesity has roughly switched- wealthier people were more likely to be obese in the 1900s, and now poorer people are more likely to be obese.
That said, muscle mass correlates almost directly with energy consumption. Muscles literally require energy to stay limp. Rigor mortis is caused by the supply of energy being cut off. The majority of the body's energy requirement is spent just keeping your muscles in working order- not even moving.
That aside, the brain burns a significant percentage of calories burned. Perhaps on whole we are thinking less?
http://www.altmedrev.com/archive/publications/11/4/278.pdf
Whatever happen to HN being a space where a legit "what if?" was explored, not knocked?
If you're sitting on your ass all day and then going out to drink a gallon of HFCS-infused coke (free refills) and a low-budget meal that could satisfy a starving family, of course you're gonna get to this point.
My personal thought with the US is "why does everything have to be so big?"
Huh? fitness industry is booming! Gym attendance is near all time highs! More and more people are eating healthier and switch to healthier and more active lifestyle.
The rates of intentional exercise - going to a gym and working out - are certainly on the rise, but the actual rate of exercise is more lower than it was a hundred years ago. The job market has switched in large part to sedentary jobs from active jobs. And diets are much less healthy today than they were then because the only diets available (to anyone other than the rich) were relatively healthy. It’s hard to become overweight without the presence of junk food. Not impossible, certainly, but hard.
I think there were a lot of these little things that mean that yes, our 'sedentary' grandparents and great-grandparents were a lot more active just because of how life was.
Unfortunately, it seems pretty predictable given the changes in our lifestyles...
I'd be careful with that assumption. Context means everything. It depends on what caused the inflammation, and what is causing its decrease.
> Economic development, improved standards of living and sanitation, decreased chronic infections from war injuries, improved dental hygiene, the waning of tuberculosis and malaria infections, and the dawn of the antibiotic age together are likely to have decreased chronic inflammation since the 19th century. For example, in the mid-19th century, 2–3% of the population would have been living with active tuberculosis (Tiemersma et al., 2011). This figure is consistent with the UAVCW Surgeons' Certificates that reported 737 cases of active tuberculosis among 23,757 subjects (3.1%). That UAVCW veterans who reported either current tuberculosis or pneumonia had a higher temperature (0.19°C and 0.03°C respectively) than those without infectious conditions supports this theory.
I would assume that less tuberculosis is a good thing (though, this being Hacker News, someone will probably show up to question that assumption too).
Tuberculosis is a disease, and widely accepted as detrimental to human health. I agree, less tuberculosis = a good thing.
This being a medically related post, more information, and less assumptions is better for everyone. Thank you for adding context.
(I welcome the downvotes! Ssssssss)
Seems reasonable that as the climate warmed by fractions, we cooled by fractions.
The general thing about the person he was responding to being totally wrong was obviously correct.
[1]: https://climate.nasa.gov/vital-signs/global-temperature/
As far as anamolies go, which area is experiencing "cooler than average" (which, as mentioned above, is difficult to do) depends on the year, but here's a map from NOAA showing 2013 temps and clearly shows the Western U.S. experiencing below average temps (from a 1980-2010 baseline): https://www.ncdc.noaa.gov/sotc/service/global/map-blended-mn...
And to underscore the situation in the 1970s I'm going to link to a documentary that starred Leonard Nemoy as narrator in 1978. Quotes below and link below to clips from:
“In Search of…The Coming Ice Age”, narrated by Leonard Nimoy (Spock from Star Trek):
“…sea coasts long free of summer ice, are now blocked year round…” “…the data shows temperatures in the arctic have fallen dramatically over the last 30 years…” “…in most locations the drop has been about 2 degrees Centigrade…”
https://youtu.be/1kGB5MMIAVA
https://youtu.be/mOC7ePWCHGk
GISS also claims to have global temperature data from 1884 that doesn't exist. They interpolate and make up numbers when they go back that far, as we don't have records from much of Asia, Africa, eastern Europe and south America during that time, even huge swaths of Australia were not covered by temperature gauges. We didn't really start getting quality global temperature data until the satellite era.
You goober, I was comparing the measurements from 2000 onward. You specifically said the past couple decades. The reference point does not matter at all.
> As far as anamolies go, which area is experiencing "cooler than average" (which, as mentioned above, is difficult to do) depends on the year, but here's a map from NOAA showing 2013 temps and clearly shows the Western U.S. experiencing below average temps (from a 1980-2010 baseline)
You just complained about cherry picking and now you're looking at a single year that was slightly colder. On average, the US is warmer everywhere.
> GISS also claims to have global temperature data from 1884 that doesn't exist. They interpolate and make up numbers when they go back that far, as we don't have records from much of Asia, Africa, eastern Europe and south America during that time, even huge swaths of Australia were not covered by temperature gauges.
Still irrelevant to the last couple decades. Sue me for trusting NASA though, I guess?
UAH is a good resource (University of Alabama-Huntsville in conjunction with NASA, albeit a different department than GISS) and they show a 0.13C per decade trend since the 80s. That being said, because global temps are not evenly distributed, some areas are experiencing cooler temps and some areas are experiencing warmer temps. Averages hide a lot of nuance. See below for latest chart from UAH:
http://www.drroyspencer.com/2020/01/uah-global-temperature-u...
https://skepticalscience.com/skeptic_Roy_Spencer.htm https://rationalwiki.org/wiki/Roy_Spencer
His own satellite work has been retracted and refuted: https://earthobservatory.nasa.gov/blogs/climateqa/have-satel...
He's a bad scientist who cares far more about his own politics than accurate research.
Also, here's more research for you to chew on:
The Key Role of Atlantic Multidecadal Oscillation in Minimum Temperature Over North America During Global Warming Slowdown
Shows minimum temps dropping during the last couple decades in North America:
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/201...
Also:
The dynamics of the warming hiatus over the northern hemisphere
https://link.springer.com/article/10.1007%2Fs00382-016-3085-...
Higher CO2 levels can reduce cognitive function [1]. Reduced cognitive function could mean reduced energy expenditure (a common figure is the brain is responsible for 20% of your energy demands), it may not though. I can see this as being a valid mental leap worth investigating.
I suspect however in this case it's a combination of the things the article suggests as well as the thermic effect of food. A reduction in the amounts of nuts/seeds/spices/whole plant foods consumed, combined with highly processed foods that require less work to digest (a piece of fruit vs a bunch of table sugar), likely means diets with a lower thermic effect from the foods. Lower thermic effect means less caloric expenditure, less caloric expenditure should mean a lower body temperature.
[1] https://ehp.niehs.nih.gov/doi/10.1289/ehp.1510037
People also became bigger during the last century which results in better thermodynamics, ie. surface/volume ratio, thus less need for burning of the internal fuel, i.e metabolic rate can be lower. Compare - elephant's 96.6 vs. cat's 101.5 body temp.
Isn't it likely that this is just a measurement/calibration/methodology error?
> As part of the study, the authors investigated the possibility that the decrease could simply reflect improvements in thermometer technology; thermometers used today are far more accurate than those used two centuries ago. “In the 19thcentury, thermometry was just beginning,” Parsonnet said.
> To assess whether temperatures truly decreased, the researchers checked for body temperature trends within each dataset; for each historical group, they expected that measurements would be taken with similar thermometers. Within the veterans dataset, they observed a similar decrease for each decade, consistent with observations made using the combined data.
Maybe the original paper discusses the point though? Perhaps they have a way to normalize temperatures to a baseline across all data sets and evaluate that way.
According to a letter Fahrenheit wrote to his friend Herman Boerhaave,[10] his scale was built on the work of Ole Rømer, whom he had met earlier. In Rømer's scale, brine freezes at zero, water freezes and melts at 7.5 degrees, body temperature is 22.5, and water boils at 60 degrees. Fahrenheit multiplied each value by four in order to eliminate fractions and make the scale more fine-grained. He then re-calibrated his scale using the melting point of ice and normal human body temperature (which were at 30 and 90 degrees); he adjusted the scale so that the melting point of ice would be 32 degrees and body temperature 96 degrees, so that 64 intervals would separate the two, allowing him to mark degree lines on his instruments by simply bisecting the interval six times (since 64 is 2 to the sixth power).
Fahrenheit soon after observed that water boils at about 212 degrees using this scale. The use of the freezing and boiling points of water as thermometer fixed reference points became popular following the work of Anders Celsius and these fixed points were adopted by a committee of the Royal Society led by Henry Cavendish in 1776. Under this system, the Fahrenheit scale is redefined slightly so that the freezing point of water is exactly 32 °F, and the boiling point is exactly 212 °F or 180 degrees higher. It is for this reason that normal human body temperature is approximately 98.2° (sic) on the revised scale (whereas it was 90° on Fahrenheit's multiplication of Rømer, and 96° on his original scale).
https://en.wikipedia.org/wiki/Fahrenheit#History
Nope: https://en.wikipedia.org/wiki/Fahrenheit#History
https://antoine.frostburg.edu/chem/senese/101/solutions/faq/...
> Changes in ambient temperature may also explain some of the observed change in body temperature over time. Maintaining constant body temperature despite fluctuations in ambient temperature consumes up to 50–70% of daily energy intake (Levine, 2007).
> Resting metabolic rate (RMR), for which body temperature is a crude proxy, increases when the ambient temperature decreases below or rises above the thermoneutral zone, that is the temperature of the environment at which humans can maintain normal temperature with minimum energy expenditure (Erikson et al., 1956).
> ... Thus, the amount of time the population has spent at thermoneutral zones has markedly increased, potentially causing a decrease in RMR, and, by analogy, body temperature.
Source: https://elifesciences.org/articles/49555
However, fevers are caused by a subset of the interleukin family, which as a whole causes inflammation. Inflammation was the author's suggestion.
Also, low grade fevers aren't a thing. Fever is caused by the immune system. You can only have a continuous infection with diseases that avoid or supress the immune system. There are a small number of brain-affecting infectious diseases like meningitis that can raise body temperature on their own. Chronically recurring stuff will also give you intermittent fevers, but there's no low-grade. You have it or you don't.
Protsiv, M., Ley, C., Lankester, J., Hastie, T., & Parsonnet, J. (2020). Decreasing human body temperature in the United States since the industrial revolution. eLife, 9, e49555.
Our average lifespan is longer than it used to be. I'd assume older people have a lower base temperature. This would skew the results statistically.
See the numerous studies that cannot be replicated, the below-the-surface iceberg of unpublished (unfavorable) studies paid for by for-profit institutions, or the shockingly small sample set or biased sample set in most studies. Most studies expose this information implicitly but it's up to the reader to determine the bias or replicate the study.
www.ncbi.nlm.nih.gov/pmc/articles/PMC6456186
Axillary (armpit) measurements, for example, are a lot colder than oral or rectal measurements. Perhaps the Russians favoured the former, while the Americans preferred the latter?
I suspect there's a nice little bell curve with 37°C in the middle.
Edit: A 37 temperature would automatically give you an excuse from school when I was a kid and, obviously, children always were finding ways to cheat. If just putting the thermometer in your mouth worked then either I was in the dark or nobody has discovered this.
When working in offices, I have noticed that people who drink pop/soda daily prefer lower room temperature than people not consuming them at all. I might have "noticed" it because of a bunch of biases, but I'd love to see a proper study on that.
You would expect the opposite of what you're suggesting, if anything. If water was used for calibrating temperature then there would be fewer good ways to control the impurity level, which would lower its freezing point. Not to mention Fahrenheit originally defined body temperature as 96 F, and it was later corrected higher.
All of the above is totally moot because we have plenty of medical thermometers from the 1900s and earlier, and they are remarkably accurate and the error is not particularly biased in either way. This is a highly researched area because the accuracy of whether thermometers is important to historical and climate research. Medical thermometers from the 1800s are good to at least 1/5th of a degree and instrumentation thermometers were good to hundredths.