In the nearly two centuries since German physician Carl Wunderlich established 98.6°F (37 C) as the standard "normal" body temperature, it has been used by parents and doctors alike as the measure by which fevers—and often the severity of illness—have been assessed.
Over time, however, and in more recent years, lower body temperatures have been widely reported in healthy adults. A 2017 study among 35,000 adults in the United Kingdom found average body temperature to be lower (97.9°F / 36.6 C), and a 2019 study showed that the normal body temperature in Americans (those in Palo Alto, California, anyway) is about 97.5°F (36.4 C).
A multinational team of physicians, anthropologists and local researchers led by Michael Gurven, UC Santa Barbara professor of anthropology and chair of the campus's Integrative Anthropological Sciences Unit, and Thomas Kraft, a postdoctoral researcher in the same department, have found a similar decrease among the Tsimane, an indigenous population of forager-horticulturists in the Bolivian Amazon. In the 16 years since Gurven, co-director of the Tsimane Health and Life History Project, and fellow researchers have been studying the population, they have observed a rapid decline in average body temperature—0.09°F per year, such that today Tsimane body temperatures are roughly 97.7°F (36.5 C).
"In less than two decades we're seeing about the same level of decline as that observed in the U.S. over approximately two centuries," said Gurven. Their analysis is based on a large sample of 18,000 observations of almost 5,500 adults, and adjust for multiple other factors that might affect body temperature, such as ambient temperature and body mass.
The anthropologists' research appears in the journal Sciences Advances.
Journal Reference:
Michael Gurven, Thomas S. Kraft, Sarah Alami, et al. Rapidly declining body temperature in a tropical human population [open], Science Advances (DOI: 10.1126/sciadv.abc6599)
(Score: 0) by Anonymous Coward on Thursday October 29 2020, @07:16PM (6 children)
I wonder if this applies to animals as well. I was reading that even lab rats, chimps, etc... have all gained weight over the last few decades or so.
I wonder if there is also a corresponding decrease in their average temperature as well.
(Score: 0) by Anonymous Coward on Thursday October 29 2020, @07:38PM (3 children)
(Same poster)
What might explain both increases in weight and reductions in temperature?
Reduced metabolic activity.
(Score: -1, Troll) by Anonymous Coward on Thursday October 29 2020, @07:46PM
If that was so, the average body temperature of lard-ass Americans on mobility scooters would be around absolute zero since it's physically impossible for them to get any larger.
(Score: 0) by Anonymous Coward on Friday October 30 2020, @02:11AM (1 child)
(same poster ... I am not the troll though)
As others have mentioned, reduced O2 concentrations could explain both.
Fire needs oxygen to burn. Likewise we need oxygen to metabolize food, burn fat, and generate heat.
Reduced oxygen concentrations could result in a reduced ability to burn fat and generate heat resulting in weight gain and lower temperatures.
A test on mice in environments with different oxygen levels (all other things constant. Same diet, same ambient temperature, same genetics) might be informative. Do the mice in environments with higher oxygen levels tend to weigh less and have higher temperatures?
(Score: 0) by Anonymous Coward on Friday October 30 2020, @01:47PM
Here, just for reference
"The obesity trend isn’t only affecting humans — chimps, pets, and lab rats are getting fatter too"
https://www.vox.com/2015/8/24/9194579/obesity-animals [vox.com]
I think this was also discussed here on Soylentnews before but I can't seem to find anything.
(Score: 0) by Anonymous Coward on Thursday October 29 2020, @08:27PM (1 child)
(Same poster)
I also wonder if an increase in the use of air conditioners has contributed to higher readings. Perhaps more people get their readings done in air conditioned buildings now.
(Score: 0) by Anonymous Coward on Thursday October 29 2020, @08:34PM
(errr ... lower readings *)
(Score: 0) by Anonymous Coward on Thursday October 29 2020, @07:20PM (23 children)
I've been about 97F for years now, on different generations of oral thermometer. With covid, I've been taking it more frequently, at random times of the day, seems to vary from 96.7 to 97.3.
My friends say I'm mellow....
(Score: 2) by DannyB on Thursday October 29 2020, @07:29PM (19 children)
My wife and I have noticed our temperatures somewhat lower.
Maybe it is not just because we're old enough to remember watching the first moon landing live?
TFA title . . .
Are we sure they are healthy?
Have the researchers controlled for Facebook usage? (I don't use FB)
To transfer files: right-click on file, pick Copy. Unplug mouse, plug mouse into other computer. Right-click, paste.
(Score: 2, Interesting) by Anonymous Coward on Thursday October 29 2020, @07:46PM (13 children)
Data (parent) here (97F +/-)...
Further details--
No FB here either (SN may be the last holdout?)
About 10 pounds heaver than I'd like to be, but still under some criteria for overweight.
I wonder if the higher atmospheric CO2 levels have anything to do with this? After all, we have chemo-receptors for CO2 that help regulate automatic breathing.
(Score: 1) by khallow on Thursday October 29 2020, @09:58PM (11 children)
(Score: 2) by dx3bydt3 on Thursday October 29 2020, @10:16PM (10 children)
That is, and has always been true, but now those variations are on top of the new higher baseline. Levels are always higher now, the peaks are higher, the average higher and the lows are higher.
(Score: 1) by khallow on Saturday October 31 2020, @04:08PM (9 children)
In comparison, outdoor concentrations increased from about 285ppm to more than 400 ppm in the past 140 or so years. Sorry, small changes in outdoor concentrations of CO2 aren't relevant.
(Score: 0) by Anonymous Coward on Sunday November 01 2020, @10:36AM (8 children)
So perhaps this is caused by a combination of the two factors.
A: People spend more time indoors than they did 100 years ago. So the oxygen concentrations they breathe are lower which results in the reduced burning of fats (more weight) and less heat that results from metabolism (lower temperature).
Also both outdoor and indoor O2 concentrations are lower. All indoor O2 comes from the outdoors so of course indoor O2 concentrations will generally be lower than outdoor concentrations. As the original poster said though if you reduce the outdoor concentrations you also generally result in reduced indoor concentrations.
"In comparison, outdoor concentrations increased from about 285ppm to more than 400 ppm in the past 140 or so years. Sorry, small changes in outdoor concentrations of CO2 aren't relevant."
That's a large increase and will increase indoor CO2 concentrations as the net gas exchange rate will now be slower. This is basic physics. The higher the outdoor CO2 concentrations the slower the indoor concentrations will get reduced due to exchange with the outside environment. The lower the outdoor CO2 concentrations the faster the indoor concentrations will get reduced due to exchange with the outside environment. Really basic physics.
What I think is relevant is the reductions in O2 concentrations. Presumably the increase in CO2 concentrations has resulted in a corresponding decrease in O2 concentrations. You also have to consider the fact that CO2 is slightly heaver than O2 (and it's more soluble in water) so it probably tends to sink towards the earth's surface (where we live) more displacing O2. So it's not like these things are proportionately distributed.
and O2 is a reactant in metabolism. Metabolism results in heat and the burning of fats. So reduced O2 concentrations may result in lower temperatures and higher weight.
An experiment with mice should probably be done to test this.
(Score: 0) by Anonymous Coward on Sunday November 01 2020, @12:04PM
Another possible reason for this could be that O2 solubility is highly dependent on temperature. Reduced O2 concentrations could be resulting in a reduction in our ability to retain enough oxygen in our bodies and so our bodies compensate by reducing the temperature in order to increase O2 solubility.
(Score: 1) by khallow on Sunday November 01 2020, @01:33PM (6 children)
I think that is even less relevant. You're speaking of a small fraction of a percent decline in O2 concentrations (oxygen concentration in comparison is about 210,000 ppm). We see more than that moving up and down a few hundred feet.
(Score: 0) by Anonymous Coward on Sunday November 01 2020, @05:04PM (5 children)
After reading more about it perhaps you have a point. It wouldn't be too difficult to conduct experiments on this though. Perhaps experiments on body temperature at different altitudes (controlling for ambient temperature of course).
Here are some studies I found might be relevant.
"OXYGEN DEFICIENCY, CARBON DIOXIDE AND TEMPERATURE REGULATION
Ernst Gellhorn"
https://journals.physiology.org/doi/abs/10.1152/ajplegacy.1937.120.1.190?journalCode=ajplegacy [physiology.org]
(unfortunately it looks like you have to pay for the rest of the info and it's an image that you can't copy and paste).
Another article I was reading through is the following
"Hypoxia is well known to reduce the body temperature (Tb) of mammals, although the neural origins of this response remain uncertain."
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2790263/ [nih.gov]
I was also looking at some of the graphs here
https://www.fondriest.com/environmental-measurements/parameters/water-quality/dissolved-oxygen/ [fondriest.com]
and reading other websites about solubility of oxygen in blood and you might have a point, it may not be a significant factor. However it's not like the temperature change is huge or drastic either so it could be a small reduction in O2 concentrations resulting in small temperature changes. It should also be noted we are looking at overall statistical data so while you may be right that it may be difficult to measure the difference in temperature caused by small differences in O2 concentrations with a small sample size the overall data may show a difference with larger sample sizes once you filter out the noise. Just because there is a difference in O2 concentrations when moving up and down a hundred feet or so doesn't make the reduced O2 concentrations any less relevant on an overall statistical scale. It just means that the O2 concentrations are lower at both altitudes and so the overall effects will be reflected in the overall readings when you take multiple samples. Even moving up or down a few hundred feet when driving can cause my ears to kinda plug until I have adjusted.
Just some thoughts. I don't really know the answer but I am trying to attack it from different perspectives.
(Score: 1) by khallow on Sunday November 01 2020, @06:05PM (4 children)
(Score: 0) by Anonymous Coward on Sunday November 01 2020, @08:56PM
On average buildings are taller now than they were 100 years ago ;)
(and, on average, hospitals are not really going to care about such a slight temperature drop)
(Score: 0) by Anonymous Coward on Sunday November 01 2020, @09:20PM (2 children)
Also CO2 is heavier than oxygen so it will tend to sink down displacing oxygen. It's not like gasses in the atmosphere are evenly distributed. Lighter gasses tend to move up relative to heavier ones. More CO2 lower down = less oxygen lower down as the heavier gas will displace it.
CO2 is also more soluble in water than oxygen.
Unfortunately when trying to do a Google search on changes in O2 concentrations over the years there is little information on the altitude of the measurements.
Reduced O2 concentrations could also be a bigger problem for enclosed regions where a lot of oxygen is being burned up and the CO2 has no place to easily escape and may sink relative to oxygen.
Overall I think you seem to have a point but I'm just trying to be thorough.
Thanks for your thoughts as well.
(Score: 0) by Anonymous Coward on Sunday November 01 2020, @09:42PM
It should also be considered that it's not like CO2 concentrations are evenly distributed across the globe either. CO2 concentrations may tend to be higher where human activity is more prevalent and this may result in reduced O2 concentrations in those areas since the CO2 may sink relative to the O2 when it first gets expelled from the sources that consume O2. So CO2 and O2 concentrations are neither evenly distributed vertically or across the globe so if we are consuming more O2 then we might be exposed to lower O2 concentrations.
So the studies intended to measure overall O2 concentrations and that notice only a slight difference because they try to filter out the noise overall may not be that relevant as the noise is what matters in these situations since the noise is where humans tend to live the most.
(Score: 1) by khallow on Monday November 02 2020, @04:28AM
The atmosphere is pretty well mixed up to the transition to the stratosphere. There's not enough CO2 to allow for such stratification with Earth weather to mix things up.
(Score: 0) by Anonymous Coward on Friday October 30 2020, @08:49AM
More likely it's decline of gut bacteria. For all we know Humans have been naturally having a lowgrade fever for all their history due to immune response in the intestimes.
(Score: 0) by Anonymous Coward on Thursday October 29 2020, @09:01PM (4 children)
uhm ... do you have an air conditioner at home compared to before? I imagine more people also have air conditioners now than before along with more buildings in general.
(Score: 0) by Anonymous Coward on Friday October 30 2020, @03:34AM (3 children)
Wouldn't explain the indigenous people, living in traditional ways, in the tropical Amazon rain forest.
(Score: 0) by Anonymous Coward on Friday October 30 2020, @12:28PM
Is there a corresponding weight gain in these people as well?
(Score: 0) by Anonymous Coward on Saturday October 31 2020, @04:19AM (1 child)
(Score: 0) by Anonymous Coward on Saturday October 31 2020, @09:35PM
That's exactly the point I was trying to make. If air conditioners are more prominent now and more temperature readings are done in air conditioned environments that might help explain the differences in readings. Thermometers start out colder. The environment is colder. You are in a colder environment so you are colder. etc... Air conditioners can also make a difference depending on where the reading is taking place (forehead, under the arms, in the mouth, etc...) as well.
Whereas heaters have been around and relatively prominent for longer than air conditioners. Even a fire can be considered a heater. Or a stove. Much older technologies in terms of when their widespread adoption has taken place so you can't really say heaters are more prominent now than before compared to air conditioners.
(Score: 2, Interesting) by hemocyanin on Thursday October 29 2020, @08:58PM (2 children)
I got a thermometer in March and it displays your temp with a color coded backlight -- white for under, green for normal, red for fever. I have to drink hot coffee to get the thing to go green, otherwise, I'm always in the white zone -- I figure if I end up in high normal, I probably have a fever.
(Score: 2, Funny) by Anonymous Coward on Thursday October 29 2020, @11:37PM (1 child)
> ...otherwise, I'm always in the white zone...
Is that like a gated community?
(Score: 2) by toddestan on Friday October 30 2020, @10:40PM
The white zone is for immediate loading and unloading of passengers only. There is no stopping in a red zone.
(Score: 2) by Snotnose on Thursday October 29 2020, @09:13PM (1 child)
I'm I think 99.4. This is a problem as every time I see a doc I have a fever. No, I just run hot. And no, I'm not bald.
My ducks are not in a row. I don't know where some of them are, and I'm pretty sure one of them is a turkey.
(Score: 0) by Anonymous Coward on Thursday October 29 2020, @09:29PM
uhm ... that's an interesting thought as well. I wonder if one can do a comparison of hair styles now compared to decades back and see if there is a trend in people now having shorter hair in general. Could something like this also help explain lower temperature readings? I do notice that my forehead temperature with the temperature gun tends to read higher sometimes when I haven't had my hair cut in a while.
(Score: 5, Interesting) by istartedi on Thursday October 29 2020, @09:27PM (1 child)
If the whole planet is really averaging warmer, then maybe bodies are responding. If the planet were constantly at a good temperature for human metabolism, would we really even need to generate excess body heat? We could go cold blooded in that case. It would only work up to a point. When things were colder, 98.6 might have provided a margin of safety that's no longer needed. Warmer ambient temperatures might allow us to run a little cooler.
It could also have nothing to do with climate. Some benign microbe might have out-competed other microbes. We might have actually been running a mild fever that whole time, to combat a hidden disease that no longer exists!
If it's a global phenomenon, it's almost certainly being driven by something global, and you don't even need to wait for evolution; just physiological response. If the Sun got brighter, our pupils would all contract too.
Appended to the end of comments you post. Max: 120 chars.
(Score: 0) by Anonymous Coward on Saturday October 31 2020, @09:43PM
If our body is producing less heat because we are in a warmer environment our body will still regulate our net temperature to the same temperature unless there is some reason for it not to. It will just use less heat/energy to do so.
To say that being in a warmer environment would result in a colder net temperature because now the body doesn't need to produce as much heat doesn't sound right. Try measuring your temperature while outside in the cold and compare that to your temperature readings while inside in a warm heated environment (wearing the same amount of clothing) and see if your temperature is warmer in the cold environment because your body is producing more heat (assuming you don't get stick and get a fever). The body produces more heat in a colder environment to compensate for heat loss in order to keep the temperature at or closer to the desired temperature.
I know my thinking is not exotic and creative, it's conventional and boring, but most of the time the boring simple answer is the best one though it's not the one that gets the most attention.
(Score: 2) by Azuma Hazuki on Thursday October 29 2020, @10:53PM
According to the optical scanners at the hospital I'm usually just over 97*F. And it's not a case of being overweight, as the scale says 128lb at 5'10". I do suspect I may be slightly hypothyroid, but taking Synthroid along with my coffee habit would probably make my heart explode...!
I am "that girl" your mother warned you about...
(Score: 4, Interesting) by legont on Thursday October 29 2020, @11:39PM
Soviet normal temperature was always 36.6 C. At 37 C I feel sick.
My bet is that 37 is just a bad science.
"Wealth is the relentless enemy of understanding" - John Kenneth Galbraith.
(Score: -1, Offtopic) by Anonymous Coward on Thursday October 29 2020, @11:50PM (5 children)
They're keeping an eye on Sleepy Joe in hope he stays above room temperature until at least January 2021. After then?
(Score: 0) by Anonymous Coward on Friday October 30 2020, @12:26AM (3 children)
I'd take sleepy Joe over the current orange man.
(Score: 0) by Anonymous Coward on Friday October 30 2020, @01:58AM (2 children)
He's orange because he takes a lot of vitamin C. Oops, wrong thread... well, this wouldn't have been off-topic, there.
(Score: 2) by hendrikboom on Friday October 30 2020, @06:05PM (1 child)
Wouldn't that be carotene?
(Score: 0) by Anonymous Coward on Friday October 30 2020, @08:38PM
Nah, that was a boy band from the '70s.
(Score: 1) by khallow on Sunday November 01 2020, @01:39PM
(Score: 2) by Revek on Friday October 30 2020, @12:06AM
I'm usually a degree low but have been as log a 96.8. When I have a 99 degree fever I'm miserable.
This page was generated by a Swarm of Roaming Elephants
(Score: 2) by sonamchauhan on Friday October 30 2020, @12:23AM (2 children)
"16 years since Gurven..."
That timespan is too low for most causes? Could the main cause be emotional?
As the world gets more materialistic, relationships deteriorate, people love less... And get physically colder in response to the subtle underlying deterioration in social relations.
(Score: 0) by Anonymous Coward on Friday October 30 2020, @01:19AM (1 child)
> Could the main cause be emotional?
Could be, but not apparently in my case. GF has been spending 4-6 weeks with her 90-year-old mother (in another state) alternating 4-6 weeks with me, for the last year or so. My oral temp doesn't change either way, although I get hugs and sleep a lot warmer when she's around (she has hot flashes...)
(Score: 2) by sonamchauhan on Friday October 30 2020, @10:23PM
:-)
I was speculating more about family breakdowns, fights, divorces, unfulfilling or tense work, increasing greed and covetousness, the single lifestyle, consumerism, chasing money.... All these stressors increasing in the past few decades.
What if introducing them to an isolated tribe (which is what happens after first contact) changed their emotions and consequently lowered their body temp in 16 years?
There is probably good reason why people are described as "cold" and "warm".
(Score: 3, Funny) by Phoenix666 on Friday October 30 2020, @01:25AM (3 children)
You guys are all missing it. It's right in front of you and you can't see it. This is proof the lizard people have been infiltrating our world and impregnating our females, thus bringing down our average body temperature.
Washington DC delenda est.
(Score: 2) by FatPhil on Friday October 30 2020, @01:50AM
Oh, sorry, you were making a joke, no? Nice one. Sorry I couldn't follow suit.
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 1, Touché) by Anonymous Coward on Friday October 30 2020, @01:57AM
Just what a lizard person would say to make it seem like a wild conspiracy theory!!
(Score: 2) by DeathMonkey on Friday October 30 2020, @07:00PM
One degree at a time sweet Jesus
One degree at a time...
Humpin' downtown in a railway station
One degree at a time..
(Score: 2) by bart on Friday October 30 2020, @10:07AM
The researchers should try to find a population whose BMI hasn't increased and do the same experiment!
(Score: 0) by Anonymous Coward on Friday October 30 2020, @11:45AM
The cause is exposure to plastics which are powerful psuedo-estrogens which confuse adrenal systems, lowering body temperatures.
High testosterone people run hotter than low test people.
Study endocrinology and you learn some interesting things!
(Score: 2) by KritonK on Friday October 30 2020, @12:24PM
A long time ago, in a galaxy far far away, back when I was little, my parents would pronounce me healthy, without a fever, if my temperature was below 37, not 37, so I don't think that this is something new.
These days, my temperature is closer to 36 than 37. This may or may not have something to do with my maintaining a weight that is on the lower end of normal for my weight and age.
(Score: 2) by hendrikboom on Friday October 30 2020, @06:07PM
My wife, who was a doctor, told me that a temperature of 36 C is pretty normal.