Is the human body getting colder? Studies reveal a decline in average body temperature

For generations, 37°C (98.6°F) has been widely accepted as the normal human body temperature. However, scientific research suggests that the average temperature of the human body has gradually decreased over the past 150 to 200 years. Studies examining historical medical records and modern temperature measurements have found that people today tend to have slightly lower average body temperatures than previous generations.

Instead, researchers believe that changes in healthcare, living conditions, infection rates and human metabolism may have contributed to the shift.

Why is average human body temperature decreasing?

One of the major studies examining this trend was published in the journal eLife in 2020 by researchers from Stanford University. The team analysed more than 677,000 body temperature measurements collected from three groups of people in the United States between 1860 and 2017.

The findings indicated that average body temperature had declined by approximately 0.03°C per birth decade. The researchers observed that people born more recently tended to have lower temperatures than those born in earlier generations.

The study challenged the long-standing assumption that 37°C is the universal average for adults. The figure originated from 19th-century research by German physician Carl Wunderlich, who analysed temperature readings from thousands of patients. Subsequent studies have suggested that the average temperature in healthy adults is somewhat lower.

Researchers have proposed several explanations for the decline. One possibility is the reduction in chronic infections and inflammation. Improvements in sanitation, access to healthcare, vaccination and the availability of antibiotics have changed the way the human body responds to infectious diseases. Since inflammation can increase metabolic activity and body temperature, lower levels of chronic inflammation may have contributed to the trend.

Changes in lifestyle and metabolism could also play a role. Modern heating and cooling systems have reduced the need for the body to expend energy to maintain its temperature in extreme environmental conditions. Differences in physical activity, nutrition and general living conditions may also influence metabolic rates.

What is considered a normal body temperature today?

Although 37°C remains a commonly used reference point, normal body temperature varies from person to person. Factors such as age, time of day, physical activity, hormonal changes and the method used to measure temperature can influence the reading.

For many healthy adults, a temperature between approximately 36.1°C and 37.2°C can fall within the normal range. Body temperature is generally lower in the morning and tends to rise later in the day.

Scientists continue to investigate the factors behind this shift and how it may reflect broader changes in human health and living conditions.

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