Human body temperature has been dropping over decades

Posted Nov 6, 2020 by Tim Sandle
Remarkably the average human body temperature has been dropping, albeit fractionally, over the past few decades. This comes from a large pool of medical data and a peer reviewed study.
Transparent woman  by an unknown artist  at the Wellcome Collection in London - the aim is to presen...
Transparent woman, by an unknown artist, at the Wellcome Collection in London - the aim is to present the human body in a different way.
The data relating to the decline in body temperature is drawn from health adults, and the analysis has been undertaken by researchers from University of California (Santa Barbara). For almost 200 years the 'normal' human body temperature has been established as 37.0 degrees Celsius (or 98.6 degrees Fahrenheit for those tied to the peculiarities of this temperature scale).
The importance of this 'norm', and of topicality in relation to the coronavirus pandemic, is with this starting point being used to measure fevers (and, conversely, conditions like hypothermia).
What appears to have been happening is that lower body temperatures are being consistently reported in healthy adults. Moreover, where 37.0 degrees Celsius seems to have been the norm for the past 180 years, over the last 20 years or so, the average body temperature as dropped. Generally this relates to data collated from the U.K. and the U.S., although more recent medical information signals the same type of decrease among the Tsimane (also known as the Chimane, who are an indigenous population who reside the Bolivian within Amazon).
As to what the new data is telling us, based on 35,000 adults in the U.K., the average body temperature is now lower at 36.6 degrees Celsius (or 97.9°F). Based on U.S. data, the drop is even more marked, at and 36.4 degrees Celsius (equivalent to 97.5°F).
However, it is the data relating to the Tsiamne population that has allowed researchers to track the temperature drop progressively, since a project has taken a series of temperatures each year (over the course of ten years). These data points indicate a relative rapid decline in average body temperature at a rate of 0.2 degrees Celsius (or 0.09°F) per year. This has led to the typical Tsimane body temperatures standing at a mean value of 36.5 degrees Celsius (97.7°F).
What has caused this shift in human physiology? The researchers speculate this is an adaptive response to modern living, where humanity has experience a lower rate of infections due to improved hygiene, clean water, vaccinations and wider coverage of medical treatment.
However, as infection rates are higher in Bolivia than the U.K. or U.S., a drop in infection rates cannot be the only explanation. This means that more study is required to understand the phenonomeon, drawing upon epidemiological and socioeconomic data.
The research has been published in the journal Science Advances, with the paper titled "Rapidly declining body temperature in a tropical human population."