Distribution characteristics of salivary cortisol measurements in a healthy young male population

• Published in: Journal of physiological anthropology Vol. 34; no. 1; p. 30
• Main Authors: Kobayashi, Hiromitsu, Miyazaki, Yoshifumi
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 19.08.2015; BioMed Central
• Subjects: Adult; Corticosteroids; Humans; Hydrocortisone - analysis; Japan - epidemiology; Male; Measurement; Reference Values; Saliva - chemistry; Short Report; Steroids; Young Adult; Japan
• ISSN: 1880-6805; 1880-6791; 1880-6805
• DOI: 10.1186/s40101-015-0068-0

Salivary cortisol has been used in various fields of science as a non-invasive biomarker of stress levels. This study offers the normative reference values of cortisol measurement for healthy young males. Salivary cortisol levels were measured in 267 healthy young males (age: 21.7 ± 1.5 years) in the early morning on two consecutive days and were analyzed by radioimmunoassay. Frequency distribution analysis was conducted with mean values of the measurements taken on the 2 days. The mean salivary cortisol level was 20.39 ± 7.74 nmol/l (median: 19.31 nmol/l). The skewness and kurtosis of the distribution of the raw data were 0.72 and 0.68, respectively. They were both improved by a square root transformation but not by a logarithmic transformation. The skewness of the distribution for salivary cortisol measured in the early morning is considerably smaller than that previously reported from afternoon measurements. A "floor effect" may be an explanation for the difference in the distribution characteristics of salivary cortisol.