Could changes in the environment lead to a change in the average body temperature? A study published earlier this month in eLife suggests that the human body is changing its normal resting body temperature in response to the changing environment.
Most of us recall that 98.6 degrees Fahrenheit/37 degrees Celsius is a normal body temperature, and we recognize anything over or under this number to represent an abnormal occurrence, such as fever. However, there is a wide range of individual body temperatures which can sometimes be higher or lower than the “standard” numbers to which we have all grown accustomed. New research has concluded that it’s not just a variance from person to person—but the average body temperature for everyone has gotten lower over the past 200 years, and it is estimated to be 97.9 degrees F/36.6 degrees C, based on a British study.
The “standard” number of 98.6 F/37 C was published by a German physician in 1868. Through an analysis of medical records in the United States, researchers determined that body temperature has been dropping through the past 200 years at a rate of 0.05 degrees F each decade. Men born in the early 1990s have an average body temperature that is 1.06 degrees F lower than the temperatures of their early-nineteenth century counterparts; while women born in the 1990s have a temperature that is 0.58 degrees F lower than the average temperature for a woman born in the late nineteenth century.
Why has this decrease in body temperature occurred in the past 200 years? Some theories make a connection between better temperatures inside our homes–as most homes two centuries ago did not have consistent heat and cooling—and the decline in body temperature. Better ambient and comfortable temperatures inside our homes and buildings allows our bodies to function at a lower metabolic rate (and thus, a lower body temperature) since we are no longer having to dedicate so much of our energy expenditure to keep body temperature stable.
Other authors in the study believe that it may be a decrease in inflammation due to better standards of living, healthier food, improved hygiene, and medical advancements which has prompted the change. The authors of the study also believe that nearly everything around us, from food to bacteria in our current environment, has changed; and we are changing along with it.
There is now a push to lower the “standard” body temperature measurement in light of these findings, which would recognize the wider range of body temperatures we see already happening between individuals.
Protsiv, Myroslava, et al. “Decreasing Human Body Temperature in the United States since the Industrial Revolution.” ELife, vol. 9:e49555, 7 Jan. 2020, doi:10.7554/eLife.49555.