American researchers analyzed the body temperature of hundreds of thousands of patients, calling into question a scientific belief that dies.
Did you think (like almost everyone else) that the normal body temperature was 37°C? This would ultimately not be completely accurate! In any case, this is what a study carried out by Stanford University and published in JAMA Internal Medicine. Professor Julie Parsonnet and her team analyzed 618,306 oral temperature measurements taken on American adults. They compared these temperatures with the patients’ health data: height, age, weight, sex, possible illnesses, etc. And excluded people who suffered from an infection. American scientists were then able to conclude that the average temperature was not 37°C. In reality, there is no average normal temperature.
“The normal temperature depends on the person and the situation, and it is rarely as high as 37°C,” explained study author Dr. Julie Parsonnet in a press release from Stanford University. Body temperature thus depends on many factors: age, height, sex, weight, time of day… These factors together represent “25% of the variability of normal temperatures within an individual and 7% of the variability from one person to another”, specify the authors of the study. They still established an average of 36.64°C.
This study is not the first to contradict the belief in the normal temperature of 37°C, which dates from the 19th century. The German doctor Wunderlich took more than a million temperature measurements from 25,000 people, and it was the average of these measurements that became the reference. But body temperature is much more variable than a simple average. Also, for many years scientists have observed that the average body temperature has been gradually falling, by around 0.03°C per decade.
This decline could be due to improvements in health care and living conditions. “These results – which are based, to our knowledge, on the largest patient sample examined to date – are consistent with numerous studies demonstrating a decline in mean normal body temperature in patients, suggesting that the canonical normal value of 37°C must be reviewed,” believes the author of the study. However, a temperature of 37°C is not synonymous with fever: this study “does not determine what can be considered abnormal or fever”, conclude the American researchers.