Hair cortisol concentration is unaffected by basic military training, but related to sociodemographic and environmental factors

Abstract

The analysis of hair cortisol concentrations (HCC) is a promising new biomarker for retrospective measurement of chronic stress. The effect of basic military training (BMT) on chronic stress has not yet been reported. The aim of this study was to investigate the effect of 10-week BMT on HCC, while further exploring the role of known and novel covariates. Young healthy male recruits of the Swiss Army participated twice, 10 weeks apart, in data collection (1st examination: n = 177; 2nd examination: n = 105). On two occasions, we assessed HCC, perceived stress and different candidate variables that may affect HCC (e.g. socioeconomic status, meteorological data). Military training increased perceived stress from the first to the second examination, but did not affect HCC. In line with this, there was no correlation between HCC and perceived stress ratings. This could be interpreted as a missing influence of mainly physical stress (e.g. exercise) on HCC. In contrast, significant correlations were found between HCC and ambient temperature, humidity and education. Future studies should control for meteorological data and educational status when examining HCC.

• Air humidity
• air temperature
• chronic stress
• education
• hair cortisol
• hypothalamic–pituitary–adrenocortical axis
• meteorological data
• sweating

Acknowledgements

The authors would like to thank the whole project team for supporting and contributing to the accomplishment of the project. A special thank you goes to the recruits of the Infantry school of Aarau, Switzerland.

Declaration of interest

This study was supported by a financial grant from the Swiss Federal Department of Defence, Civil Protection and Sport (DDPS). The authors alone are responsible for the content and writing of the paper. All authors declare that there is no conflict of interest.