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.
8 Responses
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I am 76 and have an underactive thyroid (known to slow metabolism), my temperature is usuall 97. I would like to know if my temperature escalates by 3 degrees does this mean I am running a temperature? (as it would if my temperature was normally 98.6)
Incidentally I am 6’3″ tall and my weight is 97kg (214 lbs).
Thanks for the interesting article. David
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Most medical experts feel that a fever is a temperature above 100.4 or 100.6 depending on the reference source. It is generally accepted that a fever is a significant rise from your typical basal temperature, but I am not aware that there have been any studies that have attempted to define what level of change from an individual’s typical basal temperature is defined as a fever. Part of the challenge in defining this is that even in individuals, their basal “normal” temperature can change within a 24 hour cycle. I have generally felt that a rise in basal temperature of 2-3 degrees is significant and bears watching. The higher the difference from baseline the more concerning it is, especially if there are other symptoms consistent with a concerning infection such as chills, sweats, general aches, fatigue or other constitutional symptoms.
-Dr. Sheehy
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Are the body temperatures mentioned in this article taken orally, rectally, or under the arm? And what is the typical difference in these temperatures?
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Good question. The studies mentioned in the article used different methods and instruments. Human temperatures can be measured in the mouth, ear or rectum. Ear and rectal temperatures tend to be a half a degree higher than oral temperature. Researchers who performed the studies knew this and did compensate for it to make the temperatures as accurate as possible when taken.
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My temperature usuall y has been below 98.6 all my life. When it is 98.6 , I know that I’m starting to be sick. When I am sick, my temperature goes above 102.
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So if one year old baby’s temperature is 98.7 it this considered that baby is sick?
Could you please give me more information. I have a one year old grandson and I take care of him everyday. I just want to know.
Thank you
Usha Patel-
Hi Usha,
As the article says, the body temperature of people can vary depending on different factors. 98.7 degrees is not considered a fever in a one-year old child. For children between the ages of 6 and 24 months, a rectal temperature higher than 102 F that lasts longer than one day would be considered a fever.
Note: this info came from the Mayo Clinic website:
https://www.mayoclinic.org/diseases-conditions/fever/symptoms-causes/syc-20352759
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I would agree with this study , as I’ve noticed with my own 3 kids after an illness and fever has gone away , their “normal” is around 97.5-7
I don’t know what it is regularly because I only take when I’ll and right after illness.
