By Michael Sheehy, MD
Chief of Population Health and Analytics
Reliant Medical Group
Back in 1851, a German doctor named Carl Wunderlich determined that the average human body temperature was 98.6 degrees Fahrenheit by taking the temperature of some 25,000 patients in the city of Leipzig. Although this temperature remained a standard for over a century and a half, a new study strongly suggests that the average temperature for people in the United States is not 98.6 degrees, and that human body temperatures have been slowly decreasing for decades.
Although we have all grown up thinking that 98.6 degrees is “normal,” some researchers have long thought it was too high. The recent study conducted by researchers at Stanford University and published in the online journal eLife determined that the average body temperature of Americans is closer to 97.5 degrees Fahrenheit – more than a degree lower than what most of us have believed. The study also showed that our body temperatures have consistently dropped since the 1970’s – by about 0.05 degrees Fahrenheit per decade.
The Stanford researchers looked at the temperatures of three groups including data from a study that recorded the temperatures of Civil War veterans from the mid-1800s through 1930; more recent data from the 1970’s recorded by the Centers for Disease Control and Prevention, and temperatures of patients visiting Stanford health clinics from 2007 to 2017. The data from all these studies clearly showed that average human body temperatures had dropped since Dr. Wunderlich’s landmark study in 1851. (Note that body temperature can vary depending on age, gender, time of day, and other factors.)
Researchers and scientists are not exactly sure what is causing the change in temperature. One theory is that people have grown taller and heavier over time, causing metabolic rates to slow. Improvements in overall health may also be contributing to the decline. Modern medicine has been able to greatly reduce diseases that used to be common such as syphilis, tuberculosis and periodontal (gum) disease. These diseases cause inflammation in the body, resulting in higher temperatures overall. Some researchers also believe that air conditioning and heating, which makes our environments more regulated, could also play a role.
Whatever the reason, there’s no doubt that our average body temperature is no longer 98.6 degrees Fahrenheit.