What's Behind The Strange Drop in American Body Temperatures Over The Past 200 Years?
... Early last year, researchers in the United States combed Civil War veteran records and national health surveys and found temperatures among men born at the turn of this century were 0.59 degrees Celsius cooler than those men born around two hundred years earlier.
Women, on the other hand, had seen a 0.32 degrees Celsius decline since the 1890s.
At the time, the authors suggested it might have something to do with inflammation due to disease, which is closely tied to body temperature. With the rise of modern medicine, we've seen a decline in chronic infections, and maybe, the authors suggested, this has chilled us out, so to speak.
Later in 2020, another group of researchers found an eerily similar reduction in body temperature among a relatively remote indigenous tribe in Bolivia, where infections have remained widespread and medical care minimal, despite some modern changes.
The reasons for the recent decline in body temperature clearly had to go beyond improved hygiene, cleaner water, or improved medical care, and some researchers at Harvard are now investigating another explanation: a decline in physical activity.
When a person exercises regularly, it often coincides with an increase in their metabolism. This, in turn, can raise their body's resting temperature for hours or even up to a day, which means falling body temperature measurements might indicate falling physical activity.
Unfortunately, the methods we have for measuring physical activity today weren't around 200 years ago, so we can't really compare how we move now to how we moved then.
What could be possible, however, is to use historical body temperature data as a "thermometer" to gauge physical activity before we started keeping track of these things.
If we can model the relationships between physical activity, metabolism, and body temperature we could theoretically work backward. ...
