A new study conducted by Stanford University revealed that the average human body temperature is decreasing, challenging the long-held standard established in the 19th century. Led by Dr. Julie Parsonnet, an expert in infectious diseases, the research analyzed data spanning nearly two centuries and concluded that the commonly accepted average temperature of 36.6 degrees Celsius is incorrect.
Dr. Parsonnet's team at Stanford University worked with 618,306 measurements of oral temperature from adult patients taken between 2008 and 2017. Using machine learning algorithms to eliminate data affected by diseases, the researchers conducted an extensive analysis of body temperature trends over time. The study was published in the scientific journal eLife.
The study found that normal human body temperature naturally varies between 36.2°C and 36.8°C (97.3°F and 98.2°F), suggesting that the commonly accepted value may be too high. "Most people, including many doctors, still think that everyone's normal temperature is 36.6 degrees. In fact, what's normal depends on each person and the situation; it's rarely 36.6 degrees," stated Parsonnet, a professor of medicine and epidemiology at Stanford University.
Parsonnet and her team discovered that each decade since the 19th century, the average body temperature of people in the US decreased by at least 0.05 degrees Celsius, attributed to improvements in living conditions and the general health of the population. "Physiologically, we are simply different from what we were in the past," Dr. Parsonnet stated.
The decrease in average body temperature could be linked to improvements in public health and a lower incidence of chronic infections compared to the 19th century, as well as advancements in healthcare that have reduced chronic degradation in individuals, reported El Universal. "Instead of thinking of a distribution of temperatures, which is what the initial study showed, we took an average of 36.6 degrees and used it as a cutoff value," explained Catherine Ley, lead author of the research from Stanford University, according to La Nacion.
This modification in average body temperature has implications for diagnosing conditions like fever, which may vary depending on each individual's normal temperature range. Individualized measurement of body temperature could identify deviations that might indicate the onset of a disease before other symptoms appear, according to Infobae.
Body temperature varies throughout the day and can fluctuate by a few tenths of a degree, influenced by factors such as age, weight, height, sex, and time of day, as reported by OK Diario. Body temperature tends to decrease with age, with older adults experiencing slightly lower temperatures possibly due to less muscle mass and changes in metabolism, according to Infobae. "People are cooling down," Parsonnet suggested, according to La Voz del Interior.
Women, due to hormonal changes such as those occurring during the menstrual cycle, have a slightly higher body temperature than men. Persistent deviations outside the healthy range of body temperature may be signs of medical conditions such as infections or metabolic problems, according to OK Diario.
This article was written in collaboration with generative AI company Alchemiq