Previous studies believed older measurements of human body temperature at 98.6F (37.0C) were wrong but a new has found a 0.03C cooling for every decade later someone is born. The average body temperature in the study is 36.41C (97.5F).
Men born in the early 19th-century display temperatures 0.59 degrees Celsius higher than men today, representing a decrease of 0.03 degrees Celsius per birth decade. Women’s temperatures have gone down 0.32 degrees Celsius since the 1890s, representing a 0.029 degree Celsius decline per birth decade—a rate similar to the one observed among male patients.
Factors that might be causing overall human body temperature cooling:
* Reduction of inflammation-causing conditions like tuberculosis, malaria and dental diseases, thanks to improvements in medical treatments, hygiene standards and food availability. In the 1800s 2-3% of the population would have active tuberculosis.
* Living in temperature-controlled houses
The researchers studied 677,423 temperature measurements, collected over the course of 157 years and covering 197 birth years.
There will need to be follow up studies using fitness or health monitors that can track body temperature. There will also need to be studies of people in developing countries. If there are countries where there is more inflammation-causing diseases and less temperature-controlled housing then we need to see what the variation is in body temperature.
There are some studies which show that people in Japan have body temperatures that are 0.15-0.35C lower than other people. Japan’s official body temperature is 36.0 C.
Body temperature also changes throughout the day from 36.2 to 37.5C in a 1999 study. It is lowest at night and highest during the afternoon.