Decreasing human body temperature in the United States since the industrial revolution.

Myroslava Protsiv,Julie Parsonnet,Trevor Hastie,Joanna Lankester,Catherine Ley

doi:10.7554/elife.49555

Abstract

In the US, the normal, oral temperature of adults is, on average, lower than the canonical 37°C established in the 19th century. We postulated that body temperature has decreased over time. Using measurements from three cohorts--the Union Army Veterans of the Civil War (N = 23,710; measurement years 1860-1940), the National Health and Nutrition Examination Survey I (N = 15,301; 1971-1975), and the Stanford Translational Research Integrated Database Environment (N = 150,280; 2007-2017)--we determined that mean body temperature in men and women, after adjusting for age, height, weight and, in some models date and time of day, has decreased monotonically by 0.03°C per birth decade. A similar decline within the Union Army cohort as between cohorts, makes measurement error an unlikely explanation. This substantive and continuing shift in body temperature-a marker for metabolic rate-provides a framework for understanding changes in human health and longevity over 157 years.

Highlights

In 1851, the German physician Carl Reinhold August Wunderlich obtained millions of axillary temperatures from 25,000 patients in Leipzig, thereby establishing the standard for normal human body temperature of 37 ̊C or 98.6 ̊F (Mackowiak, 1997; Wunderlich and Sequin, 1871)
Temperature measurements were significantly higher in the UAVCW cohort than in NHANES, and higher in NHANES than in Stanford Translational Research Integrated Database Environment (STRIDE) (Figure 1; Figure 1—figure supplement 1)
Analysis using body mass index (BMI) and BMI adjusted for height produced similar results (Figure 1—figure supplement 2) and analyses including only white and black subjects (Figure 1—figure supplement 3) showed similar results to those including subjects of all ethnicities

Summary

Introduction

In 1851, the German physician Carl Reinhold August Wunderlich obtained millions of axillary temperatures from 25,000 patients in Leipzig, thereby establishing the standard for normal human body temperature of 37 ̊C or 98.6 ̊F (range: 36.2–37.5 ̊C [97.2- 99.5 ̊F]) (Mackowiak, 1997; Wunderlich and Sequin, 1871). Remaining unanswered is whether the observed difference between Wunderlich’s and modern averages represents true change or bias from either the method of obtaining temperature (axillary by Wunderlich vs oral today) or the quality of thermometers and their calibration (Mackowiak, 1997). Wunderlich obtained his measurements in an era when life expectancy was 38 years and untreated chronic infections such as tuberculosis, syphilis, and periodontitis afflicted large proportions of the population (Murray et al, 2015; Tampa et al, 2014; Richmond, 2014). These infectious diseases and other causes of chronic inflammation may well have influenced the ‘normal’ body temperature of that era

Methods

Results

Conclusion