If, like me, you have always taken 37°C (98.6°F) to be the human body's average, and therefore target, temperature, you may have been labouring under a misapprehension.
The widely-used 37°C metric actually dates back to 1850, when a German physician took a survey of the armpit temperatures of 10,000 people. However, back in the 19th century, people typically had poor hygiene, low life expectancy, and chronic diseases like TB and autoimmune conditions were rife, all of which resulted in a slightly higher body temperature. As we have become generally healthier over the last 170 years, our average body temperature has also fallen.
A new study of 100,000 individuals by a Dutch doctor suggests that a better guide to average body temperatures would be 36.4°C (97.5°F), and even this is falling by about 0.03°C (0.05°F) each decade that passes. This also has implications for the clinical definition of fever, which is usually taken to be 38.4°C (101°F).
It should also be noted that body temperatures naturally change throughout the day, with night and morning temperatures lower than evening temperatures. Also, menstruating women tend to have higher temperatures, older people tend to have lower temperatures, etc, so this is not a very exact science.
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