Written by Jacob Liu and Edited by Olivia Cooper
Whether somebody is running a fever or chilled to the bone, one’s body temperature is an important indicator of health. Body temperature is dependent on a variety of factors and related to the body’s metabolic processes that contribute to the ability to produce and disperse heat [1]. That being said, when asked for a standard body temperature, most people would say 98.6 °F or 37°C, and most physicians would give a range of 97.2 °F (36.2°C) to 99.5°F (37.5°C) [2]. This value has been a constant since 1851, when German physician Carl Reinhold August Wunderlich obtained temperature measurements from 25,000 patients in Leipzig and averaged them to determine the standard for a normal body temperature [2]. However, nearly 200 years later, the conclusions of 27 modern studies reported a mean average temperature that is consistently lower than Wunderlich’s original estimate [2]. This discovery was further explored by the Stanford School of Medicine and the Tsimane Health and Life History Project (THLHP), which has conducted biometric analysis of the Tsimane Amerindians of the Bolivian Amazon since 2002 [3].
The Stanford School of Medicine analyzed 83,900 temperature measurements obtained between 1862 and 1930, another 5,998 measurements obtained between 1971 and 1975, and 230,261 temperature measurements obtained between 2007 and 2017 [2]. Altogether, the data demonstrated that for both men and women, the trend in body temperature steadily decreased over the period of analysis [4]. The question as to whether this trend was statistically significant was addressed by statistical tests of correlation, which indicated a statistically significant decrease of approximately 0.03 °C per decade [4].
To address questions of differences in temperature measurement, such location, a supplementary article from the University of Aizu described the types of body temperature measurement as core, surface, oral, and basal body temperatures, and how to adjust for the differences from these regions [5]. The THLHP also contributed to these conclusions, reporting an even higher trend of decline of 0.05°C per year over an independent study over 16 years of biometrical analysis [3]. The THLHP investigated possible reasons for the indigenous tropical Tsimane people’s temperature decline, one possible rationale being an increase in antibiotic usage, resulting in longer average life expectancy and lower body temperature as the body worked less to combat infections [3]. The studies by Stanford and the THLHP measured the recent trend of decreasing human body temperature and proposed their own testable explanations and future research directions for this phenomenon. However, this research will face the challenge of shifting a standard paradigm of such ubiquitous use, as well as questions of how the standard should be changed, who decides it, and how much research it can be structured upon. That being said, in the current state of understanding, the novelty of this phenomenon must be emphasized. This might only be indicative of a possible new standard shift, and thus calls for future research and examination of the drop in average human body temperature.
References:
- “Body Temperature: What is (and Isn’t) Normal?” Health Essentials, Cleveland Clinic, 2020, Accessed 27. Jan. 2021. health.clevelandclinic.org/body-temperature-what-is-and-isnt-normal/.
- Protsiv, M., Ley, C., Lankester, J., Hastie, T., Parsonnet, J. (2020). Decreasing human body temperature in the United States since the Industrial Revolution. eLife, 10:1-11.
- Gurven, M., Kraft, T.S., Alami, S., Adrian, J.C., Linares, E.C., Cummings, D., Rodriguez, D.E., Hooper, P.L, Jaeggi, A.V., Gutierrez, R.Q., Suarez, I.V., Seabright, E., Kaplan, H., Stieglitz, J., Trumble B. (2020). Rapidly declining body temperature in a tropical human population. Science Advances, 6:1-8.
- Weintraub, Karen. “Are Human Body Temperature Cooling Down?” Scientific American, Springer Nature America, Inc., 2020, Accessed 27. Jan. 2021.
www.scientificamerican.com/article/are-human-body-temperatures-cooling-down/. - Chen, W. (2019). Thermometry and interpretation of body temperature. University of Aizu, 9:3-17.