- Researchers have found that the average body temperature in the U.S. has fallen nearly a full degree since the early 1800s.
- In the era of nano-medicine on the cellular level, accurate standards are more important than ever.
- This study concludes that everyday inflammation in the past likely explains the difference.
Interesting Engineering reports the average human body temperature has fallen gradually over time. Using hundreds of thousands of reported temperatures from the last 150 years, scientists made a linear plot that shows our temperature has dropped 1/20th of a degree Fahrenheit per decade.
The 98.6 degrees Fahrenheit standard was established in 1851, and scientists from Stanford are saying now that it’s out of date and inaccurate for people in 2020. In their paper, they describe analyzing samples of U.S. body temperatures from three large collections of U.S. government data between 1860 and and 2017. Something that sparked their research was a meta-analysis of 27 modern temperature studies where patients uniformly fell below the 98.6-degree mark, indicating that something was rotten in the state of basal body temperature.
The three sets of data they brought in to analyze against their hypothesis were: U.S. Union veteran statistics from periodic checkups between 1860 and 1840; National Health and Nutrition Examination Results from the early 1970s; and compiled data in the Stanford Translational Research Integrated Database Environment from 2007 to 2017.
With hundreds of thousands of data points, they calculated body temperature compared with birth years and found that the average body temperature in men and women has gone down .05 degrees Fahrenheit per birth decade. When they isolated the Union veteran data, they found the same trend within that group over the long scope of their medical documentation.
This pool of data is huge, but it’s somewhat asymmetrical, with 84,000 data points over 70 years and then nearly 600,000 from the 10-year period from 2007 to 2017. There are also surprising opportunities for errors simply because of the massive technological changes from the early 1800s to the present day: How were temperatures taken, and could the change be because of more precise thermometry? The researchers considered this and controlled for any variation in thermometry.
Their analysis supported the idea that body temperature has continued to fall, which leads to the next question: why? “[W]e believe the observed drop in temperature reflects physiologic differences rather than measurement bias,” they conclude, meaning something is different in people’s bodies over time. “Heat is a byproduct of metabolic processes, the reason nearly all warm-blooded animals have temperatures within a narrow range despite drastic differences in environmental conditions. […C]hange in the population-level of inflammation seems the most plausible explanation for the observed decrease in temperature over time.”
Inflammation is evidence of the body’s immune response, and it’s caused by a variety of things. The National Institutes of Health page lists bacteria, fungi, viruses, surface injuries like scrapes and punctures, and the group of inflammatory conditions that includes cystitis, bronchitis, dermatitis, and more. Heat is one of the major symptoms of inflammation.
Are these scientists suggesting that the entire population was walking around with bronchitis every day, enough to change the population’s body temperature? No. But also … kind of. Today, bacterial infections are treated with antibiotics, and while viral conditions like bronchitis aren’t usually treatable in the same way, we can immediately take anti-inflammatory drugs like acetaminophen or ibuprofen to feel more comfortable.
Bringing down swelling—the same is true of a course of steroids for an injury—reduces the extra body heat almost immediately. Cooling a fever with acetaminophen brings down your body temperature. We’re much more equipped to spot-treat these symptoms, even as the conditions themselves aren’t gone yet. Even injuries like sprains, which usually aren’t serious and resolve on their own, cause temperature-boosting inflammation.
Your temperature is falling—and the reason is just over the counter.