“We’re getting cold”: the study conducted by Julie Parsonnet, a doctor specializing in infectious diseases at Stanford University, is formal.
An interval of 1.5 ° C
Today, 36.5 ° C should be considered the “norm” for a healthy human body, he says – and that any temperature between 35.7 and 37.3 ° C should be considered normal, the researchers recall.
To function properly, the body must in fact remain within a temperature difference of about 1.5 ° C. Outside, the neurons, the organs, the muscles work less well. The body therefore consumes a lot of energy to stay at this temperature level.
All this happens through signals emitted by the hypothalamus, which warn us that our blood is not at the right temperature.
Julie Parsonnet, researcher at Stanford
Many factors have an influence: age, morphology, activity, diet, time and method of measurement, etc. An infection, of course, can also cause the temperature to fluctuate, to help the immune system fight pathogens.
Initially, Julie Parsonnet worked on Americans weight gain. By studying 200,000 measurements spread over 160 years, she found that the body temperature of an “average” American had dropped 0.5 ° C (or 1 ° Fahrenheit) in the meantime. Data that amply justify, according to her, the need to re-evaluate the considered “normal” level of this temperature:
We got taller, fatter, and colder [nous vivons] Longer. These four elements go together, in a sense
An error with the thermometer in question?
Faced with Julie Parsonnet’s results, Philip Mackowiak defends this hypothesis. Professor Emeritus at the Medical University of Maryland, he thinks it is … the starting reference to be inaccurate: the famous “37 ° C” dates back to an 1871 book, published by the German physician Carl Rinhold August Wunderlich. Which would have reached an average of one million temperatures accumulated over the years of practice in a clinic.
Mackowiak points to two pitfalls: the fact that he was able to achieve an average, at the time, over such a large set, without a computer. And the weakness of the mercury thermometers of the time. Pr Mackowiak examined the instrument used, exhibited in Philadelphia:
[Il] it was calibrated at 1.5 degrees [centigrade] more than modern or contemporary thermometers
What invalidates Julie Parsonnet’s theory? Refusing to decide, he says he is “not convinced” of her work, but doesn’t close the door – and also disputes 37 ° C as a reference:
I have no way of being sure, one way or the other. But my intuition is no. [la température corporelle humaine] it has not diminished over time
Other researchers, not necessarily convinced at first, joined the Stanford scientist. Like the anthropologist Michael Gurven of the University of California, who reanalyzed all the data. And I got the same result:
We don’t understand exactly why, but there appears to be a decline
He wanted to see if the evolution of lifestyles could play a role. Working on the people of Chimanes, a population of Bolivia quite isolated from the outside world, he also noticed a decrease from 37 to 36.5 … but in just 20 years! Without being able to explain it until today, both for this people and in general.
Among the possible causes, air conditioning, nutrition, chronic diseases, parasites, sleep habits, drugs … The simple fact of better access to the health system or to some basic necessities could play a role. , like blankets.
Should we worry about 37 ° C?
Researchers insist on the need to evolve with respect to the immutable reference of 37 ° C, at least in the medical field. However, they remind us: at 36.5 ° C or 37 ° C there is no fever.
37 ° C is a normal temperature, but it is not “the” normal temperature
Today, in the hospital, one generally qualifies as a fever above 38.3 ° C (101 ° F). But this is never the only symptom observed by nurses:
Fever is only one of the indications of the disease. But the fact is, if you feel bad, then you are sick, no matter what your temperature is.