Health

Think 98.6 degrees is normal body temperature? Coe College study confirms it's not

Coe alum's 40-year habit compelled body-temp revelations

A study by Coe College alumna Rebecca Anderson published in Biological Rhythm Research journal indicates, among other things, that the human body’s temperature rarely is at 98.6 degrees Fahrenheit, rebuffing conventional wisdom. (Morguefile)
A study by Coe College alumna Rebecca Anderson published in Biological Rhythm Research journal indicates, among other things, that the human body’s temperature rarely is at 98.6 degrees Fahrenheit, rebuffing conventional wisdom. (Morguefile)

Forty-three years ago, in 1976, the United States was celebrating its bicentennial, and Fort Madison native Rebecca Anderson was getting into the celebratory spirit from Canada, of all places.

The 26-year-old Coe College alumna was taken by the plethora of patriotic projects underway to commemorate the 200th anniversary of her country’s independence — from time capsules and television specials to parades, postage stamps, and pyrotechnics.

“That mind-set was in the air, and I got to thinking … what could I do as a forward-thinking project that would provide some contribution?” Anderson said.

What she came up with produced 30-plus years of unique and unconventional data that laid the groundwork for an analysis published last month in the Biological Rhythm Research journal indicating, among other things, that the human body temperature rarely is at 98.6 degrees Fahrenheit — rebuffing conventional wisdom.

“That was one of the more interesting findings, that most of the time, 98.6 probably isn’t the target normal temperature,” Anderson, now 69, told The Gazette. “And what really surprised us is there is a slow and noticeable decrease in body temperature throughout life.”

Anderson, who now serves on an advisory council for Coe, facilitated that nugget of corroborating biological insight — and others — by deciding in conjunction with the bicentennial to add one small habit into her daily routine. Every night, before heading to bed between 11 and 11:30 p.m., she would take her temperature and log the data.

Anderson used an old-fashioned mercury thermometer and jotted down any extraneous factors potentially affecting the data — like if she was traveling, battling an illness, or menstruating.

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“I wasn’t sure that it would lead to anything,” Anderson said. “But I thought that if I took enough data over a long enough period of time, that certainly would be a rare set of data.”

Still, upon starting the bedtime routine in her 20s, Anderson hadn’t planned to continue for three decades.

“In the end, I did.”

Until at age 56, Anderson decided she’d tracked her temperature long enough and reached out to Coe College mathematics professor Gavin Cross to gauge his interest in mining the numbers either for new information or for confirmation of more speculative research that could benefit from corroboration.

Cross told The Gazette, as a statistician, he was happy for the expansive data and — in his analysis — discovered both.

The Anderson data set confirmed existing research showing the human body temperature is rarely at 98.6 degrees and also declines gradually as a person ages. Anderson experienced a progressive dip of .1 degree every three years throughout adulthood, with her average body temperature at age 55 reaching 97.3 degrees, according to the study.

That, according to Cross, is consistent with other published studies reporting the average body temperature of older adults.

The Anderson data also confirmed previous research revealing menopause can accelerate the drop in temperature — information Cross gleaned after his subject decided to go back postmenopause, from age 60 to 61, to collect two more years of nightly temperatures.

New findings revealed by the Anderson data that had not been widely studied before relate to seasonal variations in body temperature — regardless of geographic region — and the impact of daylight saving time.

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Over her 30 years collecting temperatures, Anderson lived in Canada, on the East Coast, and eventually on the West Coast — where she lives today, in Santa Barbara. Regardless of the region, Cross said, Anderson’s body temperature was highest in August and lowest in February.

“About a quarter of a degree,” he said. “And that was steady no matter where she lived.”

The data also revealed Anderson’s body took about four days to react to the change of daylight saving time. In the spring, Cross said, her temperature rose about half a degree before coming back down four days later. In the fall, it dipped about .2 degrees before adjusting back after four days.

“The shock of daylight saving time from before to after really does influence a body’s physiology,” Anderson said. “It’s a subtle thing. But clearly there are things going on in your body that are impacted by that time shift.”

Although Anderson aimed in her data collection to remain consistent with when she took her temperature, that didn’t always happen — as she occasionally had to squeeze it in earlier or log it later than planned. And, Cross said, that actually proved helpful, in that he was able to extrapolate from those variations that temperature actually decreases over the course of the evening and into night.

“Your body has these rhythms throughout the day,” he said. “And there are these decreases when you are getting into sleep mode.”

The information also confirmed the widely-circulated knowledge that female body temperature increases during menstruation. However, it showed considerable variation from one cycle to the next, stripping away its reliability as an indicator of when a person is ovulating, according to Anderson.

Beyond that finding, Cross and Anderson said the data — and any corroborating research it might compel — could have lasting implications for the medical profession and other fields. If, for example, doctors continue using 98.6 degrees as the normal body temperature, without speculation, they could miss a slight fever — especially in the elderly population.

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“That could lead to some misdiagnoses or not clear understanding of what is happening with a patient,” Anderson said.

l Comments: (319) 339-3158; vanessa.miller@thegazette.com

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