Forget 98.6°F humans are cooling off — here’s why

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THE 98.6°F standard was established by a German doctor in 1851. Recent studies have indicated that’s too high. Getty Images
A German physician came up with 98.6°F as “average” human temperature in the 1800s.
Now researchers say the average human temperature is lowering slightly.
The reasons for this could be less inflammation among today’s population.
The “normal” body temperature of 98.6°F (37°C) is actually not so normal. New research finds the average human body temperature of Americans has dropped.
“What everybody grew up learning, which is that our normal temperature is 98.6, is wrong,” said Dr. Julie Parsonnet, a professor of medicine as well as health research and policy at Stanford University School of Medicine.
The 98.6°F standard was established by a German doctor in 1851. Recent studies have indicated that’s too high; research on 35,000 British people found their average was 97.9°F.
Parsonnet’s study published this week in eLife. It found that temperature changes since 1851 reflect a historical pattern instead of an error. They contend the decrease is the result of environmental changes over the past 200 years that have affected human physiology.
Parsonnet looked at data from 1862 through 1930, 1971 through 1975, and 2007 through 2017. It included 677,423 temperature measurements.
The body temperature of men born in the 2000s is 1.06°F degrees lower, on average, than men born in the early 1800s. Women have temps about 0.58°F lower than those born in the 1890s. That means body temperatures declined 0.05°F every decade.
Parsonnet’s team also found a decline in temperature since the 1960s, not just since the Civil War.
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Body temperature is complicated, Parsonnet says. It can vary not just from person to person but at different times of day and at different ages.
It can be almost half a degree higher in the afternoon than morning. It’s much lower in older adults. Your weight and height as well as hot or humid weather can also affect it, Parsonnet says.
In her experience, Parsonnet says at least 75 percent of normal temperatures are below 98.6°F.
“Even in younger adults at the end of the day, when temperatures are at their highest, the temperature still doesn’t get up to 98.6,” she said.