Humans are cooling down so average body temperature is no longer 37°C

Study at Stanford University: “body temperature in men and women, after adjusting for age, height, weight and, in some models date and time of day, has decreased by 0.03°C per birth decade.”

Body temperature has decreased over time. The normal, oral temperature of adults is lower than 37°C which established in the 19th century,  a study at Stanford University, School of Medicine, published in Life Science, report.

In 1851, the German physician Carl Wunderlich obtained millions of axillary temperatures from 25,000 patients in Leipzig, thereby establishing the standard for normal human body temperature of 37°C or 98.6 °F vs. oral today.

Researchers crunched numbers from three studies that provided

The new study led by Myroslava Protsiv, compared data of three cohorts collected 677,423 temperature measurements over 157 years between 1860 – 2017 from collections of U.S. government data. The Union Army Veterans of the Civil War (23,710  individuals measurement years 1860–1940); the National Health and Nutrition Examination Survey I ( 15,301 individuals; 1971–1975), and the Stanford Translational Research Integrated Database Environment (150,280 individuals; 2007–2017)- determined that body temperature in men and women, after adjusting for age, height, weight and, in some models date and time of day, has decreased by 0.03°C in each passing decade.

In addition, they used a statistical analysis that combines the results of the latest 27 temperature studies where patients uniformly fell below 37°C or 98.6 °F, indicating that something wrong in the state of basal body temperature.

Wunderlich obtained his measurements in an era when life expectancy was 38 years and untreated chronic infections such as tuberculosis, syphilis, and periodontitis contaminated a large population. These contagious diseases, and other causes of chronic inflammation, may well have influenced the ‘normal’ body temperature of that era.

The question of whether mean body temperature is changing over time is not just a matter of curiosity. Human body temperature is a crude surrogate for a basic metabolic rate which has been linked to both longevity and body size.

The team speculated that the differences observed in temperature between the 19th century and today are real and that the change over time provides important physiologic clues to alterations in human health and longevity since the Industrial Revolution.

Study co-author Julie Parsonnet, professor of medicine and of health research and policy at Stanford University School of Medicine, said in a statement: “Inflammation produces all sorts of proteins and cytokines that rev up your metabolism and raise your temperature.

“Physiologically, we’re just different from what we were in the past. The environment that we’re living in has changed, including the temperature in our homes, our contact with microorganisms and the food that we have access to,” she said.

“All these things mean that although we think of human beings as if we’re monomorphic and have been the same for all of human evolution, we’re not the same. We’re actually changing physiologically.”

“Our temperature’s not what people think it is. What everybody grew up learning, which is that our normal temperature is 98.6, is wrong,” she added.

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