It is one of those facts of life that we learn early and don't forget: normal body temperature is 98.6 degrees Fahrenheit. But a new study in eLife argues that that number is outdated. The figure was probably accurate in 1851, when German doctor Carl Reinhold August Wunderlich found it to be the average armpit temperature of 25,000 patients. Times have changed, though, according to the recent paper: the average American now seems to run more than a degree F lower.
Stanford University researchers looked at data from Civil War soldiers and veterans and two more recent cohorts to confirm that body temperatures among American men averaged around 98.6 degrees F back then but have steadily fallen over time and that temperatures among women have fallen as well. Their data find an average for men and women of 97.5 degrees F.
The study suggests that in the process of altering our surroundings, we have also altered ourselves, says senior author Julie Parsonnet of Stanford. The researchers did not determine the cause of the apparent temperature drop, but Parsonnet thinks it could be a combination of factors, including warmer clothing, indoor temperature controls, a more sedentary way of life and—perhaps most significantly—a decline in infectious diseases.
