Average Human Body Temperature Declines Over 150 Years
Recent studies indicate a gradual decrease in average human body temperature, challenging long-held beliefs.
Average body temperature has decreased by about 0.03°C per decade since the 1860s.
Factors such as improved healthcare and reduced chronic infections may contribute to this trend.
Normal body temperature now varies, with healthy adults averaging between 36.1°C and 37.2°C.
For over a century, 37°C (98.6°F) has been regarded as the standard for normal human body temperature. However, recent scientific investigations reveal that this average has been declining over the past 150 to 200 years. Research analyzing historical medical records alongside contemporary temperature data indicates that individuals today generally exhibit slightly lower body temperatures compared to their predecessors.
A significant study published in the journal eLife in 2020 by a team from Stanford University examined over 677,000 body temperature readings from three distinct groups in the United States, spanning from 1860 to 2017. The results showed a decline of approximately 0.03°C for every decade of birth, with more recent generations exhibiting lower average temperatures than those born earlier. This challenges the long-standing belief that 37°C is the universal norm for adults, a figure originally established by German physician Carl Wunderlich in the 19th century based on extensive patient data.
Several factors may explain this observed decline in body temperature. One hypothesis suggests that advancements in healthcare, including improved sanitation, vaccination, and antibiotic availability, have led to a decrease in chronic infections and inflammation, which can elevate metabolic rates and body temperature. As chronic inflammation diminishes, it is plausible that average body temperatures have also decreased.
Lifestyle changes and modern conveniences may further influence body temperature. With the advent of heating and cooling technologies, the human body no longer needs to expend as much energy to regulate its temperature in extreme conditions. Variations in physical activity levels, dietary habits, and overall living conditions could also impact metabolic rates and body temperature.
While 37°C is still a commonly referenced benchmark, normal body temperature is now understood to vary among individuals. Factors such as age, time of day, physical exertion, hormonal fluctuations, and measurement methods can all affect temperature readings. For many healthy adults, a range of approximately 36.1°C to 37.2°C is now considered normal. Ongoing research aims to further explore the implications of this temperature shift and its potential connections to broader health and environmental changes.
