One of the most common assumptions people make when checking for a fever is that a person’s normal body temperature is always 98.6ºF (37ºC). It’s not, reports Wired.
In fact, there is no specific degree that is normal or common for everyone; body temperatures are flexible, changing with age, gender, and time of day, weather, medication, reproductive cycle and more, according to Jonathan Hausmann, a rheumatologist at Boston Children’s Hospital and Beth Israel Deaconess Medical Center in Boston, US. Women’s typical body temperatures run slightly higher than men’s, and children’s temperatures run higher than adults. But even that rough standardization doesn’t hold steady, as body temperature fluctuates throughout the day for everyone — starting low in the morning, and rising as the day progresses.
“A temperature of 99 [F] at six o’clock in the morning is very abnormal, whereas that same temperature at four o’clock in the afternoon can be totally normal,” Haussman told Wired. He recently crowdsourced thousands of body temperatures from 329 healthy adults via an iPhone app to arrive at this conclusion.
His study, published in the Journal of General Medicine, challenges the gold standard of 98.6ºF, or 37ºC, of body temperature, which he says dates to a single study conducted in the 1800s with an unreliable thermometer. Hausmann’s research, by contrast, found an average body temperature of 97.7ºF (36.5ºC) via oral thermometer among respondents. Which means fevers might begin slightly lower than what is officially defined; for instance, the US’s Centers for Disease Control and Prevention (CDC) puts 100.4ºF as the official fever mark. But Hausmann’s research suggests the average fever may start as low as 99.5ºF (37.5ºC).
Hausmann is not the first to challenge the 98.6ºF, or 37ºC, norm; studies as far back as 1992 have suggested average body temperature might differ from general consensus. But in the age of big data and easy tech, he may succeed through prolific and quick research, where others have failed.
The irony is, in the same era, the guidance for how to tell if you have a fever is essentially the same as it was back-in-the-day. As the Wired report sums up: “If you think you have a fever, you probably do.”
The bigger question, especially when dealing with kids, is what to do about it.
