A recent study published in the journal Nature Communications has challenged the long-held assumption that there is an ideal body temperature for humans. The study, conducted by researchers from Stanford University and the University of California, San Francisco, analyzed data from over 600,000 patients who visited Stanford Health Care between 2008 and 2017. They found that body temperature varies greatly among individuals, and is influenced by factors such as age, gender, body mass index, time of day, and health conditions.
The researchers used a novel device called iButtons, which are small metal capsules that can be attached to the skin and measure temperature continuously for up to two weeks. They also developed a smart algorithm that can filter out noise and outliers from the data, and provide accurate estimates of body temperature.
The study revealed that the average body temperature of the patients was 36.6 degrees Celsius (97.9 degrees Fahrenheit), which is lower than the commonly accepted value of 37 degrees Celsius (98.6 degrees Fahrenheit). This value was first established in the 19th century by German physician Carl Reinhold August Wunderlich, who measured the temperature of thousands of patients using a 30-centimeter-long thermometer.
However, the study also showed that there is no single average body temperature for humans, as it varies significantly among individuals. For example, women tend to have higher body temperatures than men, older people tend to have lower body temperatures than younger people, and people with higher body mass index tend to have higher body temperatures than people with lower body mass index. Moreover, body temperature changes throughout the day, with a peak in the late afternoon and a trough in the early morning.
Body temperature can indicate health status and disease risk
The study also found that body temperature can be used as an indicator of health status and disease risk. The researchers discovered that people with certain health conditions, such as diabetes, hypertension, and thyroid disorders, tend to have lower or higher body temperatures than healthy people. They also found that changes in body temperature over time can predict the onset or progression of some diseases.
For instance, the study showed that people with type 2 diabetes have lower body temperatures than people without diabetes, and that a decrease in body temperature over time can precede the diagnosis of diabetes by several years. The researchers speculated that this could be due to impaired thermoregulation or reduced metabolic activity in people with diabetes.
On the other hand, the study showed that people with infections or inflammation have higher body temperatures than normal, and that an increase in body temperature over time can signal the presence or worsening of these conditions. The researchers suggested that this could be due to increased immune system activity or tissue damage in response to infection or inflammation.
The study also revealed that body temperature can be affected by environmental factors, such as ambient temperature, humidity, and season. The researchers observed that people living in warmer climates tend to have lower body temperatures than people living in colder climates, and that people tend to have higher body temperatures in summer than in winter. They explained that this could be due to adaptive mechanisms that help maintain thermal balance and prevent overheating or hypothermia.
Implications for clinical practice and future research
The study has important implications for clinical practice and future research. The researchers argued that using a fixed threshold of 37 degrees Celsius (98.6 degrees Fahrenheit) to define fever or normalcy is inaccurate and misleading, as it does not account for individual variability and contextual factors. They proposed that personalized reference ranges should be used instead, based on each person’s baseline body temperature and relevant characteristics.
The researchers also suggested that continuous monitoring of body temperature using wearable devices could provide valuable information for diagnosis, prognosis, and treatment of various diseases. They recommended that more studies should be conducted to explore the biological mechanisms and genetic factors underlying the variation and regulation of body temperature in humans.
The study was led by Dr. Julie Parsonnet, a professor of medicine and health research and policy at Stanford University School of Medicine, and Dr. Wenyu Zhou, an assistant professor of epidemiology and biostatistics at University of California San Francisco School of Medicine. The study was funded by the National Institutes of Health and the Bill & Melinda Gates Foundation.