Declines in normal body temperature (which is considered 98.6°F, a standard established by German physician Carl Wunderlich) were observed in the latest decades in some medical studies. Lower body temperatures have been widely reported in healthy adults. A 2017 study among 35,000 adults in the United Kingdom found average body temperature to be lower (97.9°F), and a 2019 study showed that the normal body temperature in Americans (those in Palo Alto, California, anyway) is about 97.5°F, as exemples. Body temperatures below 98.6°F are also found in places outside the U.S. and the U.K.
. „It was clear that something about human physiology could have changed. One leading hypothesis is that we’ve experienced fewer infections over time due to improved hygiene, clean water, vaccinations and medical treatment. In our study, we were able to test that idea directly. We have information on clinical diagnoses and biomarkers of infection and inflammation at the time each patient was seen,” was one conclusion of a study conducted by a multinational team of physicians, anthropologists and local researchers led by Michael Gurven, UC Santa Barbara professor of anthropology and chair of the campus’s Integrative Anthropological Sciences Unit, and Thomas Kraft, a postdoctoral researcher in the same department. But „reduced infection alone can’t explain the observed body temperature declines” was another observation. So other hypothesis emerged. “Another possibility is that 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,” Kraft said. As body temperature is linked to population health, there is an excitment to entirely solve the mistery.