By Dr. Dave Hnida

(CBS4) – You’ve heard of global warming. Now comes the concept of human cooling. Since 1851, we’ve used 98.6 as the gold standard of normal temperature. Turns out we’ve been chilling out each decade since then, to where now the new normal may be a degree chillier: 97.5 degrees Fahrenheit.

That’s according to new research out of Stanford University and published in the Journal eLife.

Researchers analyzed more than 677,000 body temperature measurements taken between the years 1862 and 2017. They found that the average body temperature dropped, on average, 0.05 degrees each decade since the beginning of the study period.

Why? Researchers aren’t exactly sure, but suspect it all has to do with an overall decrease in population-wide body inflammation in the years since the 1860s. That chronic inflammation early in the study years stemmed from things such as poor nutrition, poor sanitation, less hygienic living conditions, colder housing, more dental disease, and more smoldering infections such as TB.

In other words, the standard of living is steadily improving and decreasing the germs we fight off every day to keep from getting sick. And the introduction of central heating and air conditioning means our bodies don’t have to work as hard to maintain a constant body temperature.

The average life expectancy, by the way, in the 1860s was, for a male, 38 years old.

Other findings that held up throughout the 150+ year study:

Women tend to run a higher baseline temperature than men. Heavier people tend to be warmer. Taller people tend to be cooler. And body temperature rises as the hours pass over the course of a day (which helps explain why your child tends to have a higher fever at night).

As for me, this study explains a lot of things, such as my “normal” temperature averages 97.6. And if I hit 98.6, I feel chilled as if I’m starting to get a fever.

How about you? What’s your “normal temperature”?

For more info on temperature:


Dr. Dave Hnida

Comments (4)
  1. Ove Hetland says:

    In my country (Eastern Europe) at least for the last 40 years or so, 98.6 (37.0 in Cel) was never considered normal, it was always regarded as slight fever and normal was 97.7 or 97.8 (36.6).

  2. Gregory S Marlow says:

    It is probably because we sit around so much and don’t generate body heat from our muscles.

  3. “The average life expectancy, by the way, in the 1860s was, for a male, 38 years old.”That stat is actually misleading, as is the generally accepted notion that human longevity is now much greater than, say, 100 to 200 years ago. However, if you remove the infant mortality factor from the stats, you’ll find that human lifespan hasn’t increased to any great degree. The stats are being skewed by a much higher rate of infant survival in modern times.

  4. says:

    hey that’s maybe why my home thermometer shows a 97.5 most of the time; i thought it was defective and the doctor’s shows it higher; what thermometers were used in the study?

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