Levels of circulating cortisol and cytokines in members of the Canadian Armed Forces: associations with age, sex, and anthropometry

Abstract

This study assessed blood levels of cortisol and cytokines (inflammatory and non-inflammatory) in members of the regular Canadian Armed Forces (CAF), and examined the associations between sex, age, and adiposity and circulating levels of cortisol as well as pro-and anti-inflammatory cytokines. As part of a larger ranging project, 331 blood samples were collected from a representative population of the total CAF, which included officers and noncommissioned women and men from the Air Force, Navy, and Army. The blood samples were analyzed for levels of cortisol, C-reactive protein (CRP), adiponectin, and 20 cytokines (which included interleukins, interferons, and tumor necrosis factors). Higher levels of adiponectin were found in women compared with men (median and interquartile range; 16.71 (7.68-25.32) vs 5.81 (3.52-13.19) mu g/mL), and higher levels of interleukin (IL)-18 in men compared with women (89.25 (84.03-94.48) vs 75.91 (69.70-82.13) pg/mL). An association between age and levels of stress and inflammatory cytokines was observed, with CRP, IL-18, IL-2 and adiponectin all increasing with increasing age. However, contrary to trends seen in the general population, cortisol levels decreased with increasing age. Levels of CRP and IL-18 increased with an increase in adiposity, while adiponectin levels decreased. Most importantly, at the entire cohort level, a low detection rate for most of the cytokines was observed with 17 out of 22 cytokines having a detection below 10%. In conclusion: In this CAF population, although an association between age and inflammatory cytokines was observed, both sex and adiposity had a small impact on levels of cortisol and cytokines.