If I asked you about the body temperature of the average person, what would you say? Very likely, you’d say 37°C.
This wasn’t plucked out of nowhere. German physician Carl Reinhold August Wunderlich took more than a million readings from 25,000 patients at Tübingen general hospital in the mid 1860s. He believed that fever is a symptom of disease, not a disease in itself. Inflamed parts of the body have a higher temperature than the rest.
That knowledge has been refined over time. We now know temperatures vary throughout the day, being lower in the morning and peaking at around 6pm, and that there are even differences in temperatures between men and women (Danny and I have talked previously about how men and women feel temperature differently too).
But average body temperature in America has been steadily dropping about 0.02°C a decade since the 1860s and in 2017, the mean oral temperature in Britain was 36.6°C. I know my usual temperature is about 36.6°C, as is the rest of family.
It’s possible that this is due to improved health and better living conditions.
But a recent study in the Tsimane people of Bolivia has found the same thing. Their average temperature has declined by roughly 0.05°C per year since measurements began as part of the Tsimane Health and Life History Project in 2001.
It’s not clear why, but there are a few possibilities:
- lower rates of lingering mild infections (although infections are still common in rural Bolivia)
- people are in better condition, so their bodies don’t work as hard to fight off infections
- access to antibiotics and other medical treatments such as anti-inflammatory drugs means that infections last for less time than in the past
- our bodies don’t have to work as hard to regulate internal temperature because of air conditioning in the summer and heating in the winter (although the Tsimane do not use technology for helping to regulate their body temperature. They do, however, have more access to clothes and blankets).
It’s difficult to pin down the cause of changes in body temperature, but measuring changing average temperatures of entire populations could be used as an indicator of health in the overall population.
I talked about this with Danny Hoyland on West Bremer Radio on 23 April 2022. Listen each week: Saturday 7.40 am, West Bremer Radio.