Effects of Combined Stress during Intense Training on Cellular Immunity, Hormones and Respiratory Infections

Abstract

Objectives: This study was designed to determine immune and hormonal changes and their relationship with the incidence of upper respiratory tract infections (URTIs) during an extremely stressful military training (3 weeks of physical conditioning followed by a 5-day combat course with energy restriction, sleep deprivation and psychological stress). Methods: Blood samples were collected from 21 cadets (21 ± 2 years old) before training and after the combat course for analysis of leukocyte and lymphocyte subpopulations, serum cytokines [interleukin-6 (IL-6), IL-1β and IL-10], and hormones [catecholamines, cortisol, leptin, total insulin-like growth factor I (IGF-I), prolactin, dehydroepiandrosterone sulfate (DHEAS) and testosterone]. Symptoms of URTI were recorded from health logs and medical examinations during training. Results: After the combat course, total leukocyte and neutrophil counts were significantly increased while total lymphocytes were unchanged. In lymphocyte subsets, NK cells were reduced (p < 0.01), while CD4+ and CD19+ (B) cells were increased. Levels of IL-6 were increased (p < 0.01), while those of IL-1β and IL-10 were unchanged. Norepinephrine and dopamine levels were increased, while those of cortisol were reduced. Levels of leptin, testosterone, prolactin and total IGF-I were reduced, while those of DHEAS were increased. The incidence of URTI increased during the training (χ² = 53.48, p < 0.05). After training data analysis showed a significant correlation between URTIs and NK cells (p = 0.0023). Training-induced changes in immune and hormonal parameters were correlated. Conclusions: Blood NK cell levels are related to increased respiratory infections during physical training in a multistressor environment. The training-induced decreases in immunostimulatory hormone levels may have triggered immunosuppression.

Psychological stress downregulates epidermal antimicrobial peptide expression and increases severity of cutaneous infections in mice

“…While these results provide mechanistic insights into PS-related alterations in antimicrobial defense, they also provide a likely pathomechanism for the increased risk of cutaneous (and extracutaneous) infections during PS (13,15,18,20,24) as well as both systemic and topical GC therapy (47,48,57,58). It should be noted, however, that PS or GC therapy could increase the risk of cutaneous infections by other, unrelated mechanisms; for example, GCs decrease epidermal dendritic cell function (59,60), another important participant in cutaneous innate immunity, and also decrease epidermal primary cytokine levels (33), which could influence antimicrobial defense by a variety of downstream mechanisms.…”

“…Although recent studies in both humans and experimental animals suggest that PS compromises host defenses against bacterial and viral infections (13)(14)(15)(16)(17)(18)(19)(20)(21), the pathogenic mechanisms remain unknown. Three potentially interconnected mechanisms have been proposed to explain the negative impact of PS on host defenses against infection and neoplasia: (a) psychoneuroimmunoendocrine dysfunction, which leads to increased proinflammatory neuropeptide and cytokine production in a manner either dependent or independent of the hypothalamic-pituitary-adrenal (HPA) axis (18)(19)(20)(21)(22)(23)(24); (b) increased plasma levels of endogenous glucocorticoid (GC) caused by activation of the HPA axis (16, 18-21, 24, 25); and (c) a cutaneous steroidogenic system, with localized production of corticotropin-releasing factor (CRF) (26,27), which could mediate the adverse effects of PS on skin.…”

The effect of deployment to a combat zone on testosterone levels and the association with the development of posttraumatic stress symptoms: A longitudinal prospective Dutch military cohort study

“…Alterations were also found after a prolonged period of stress exposure. Decreased plasma testosterone levels were found during and after 3 weeks of military training followed by a 5-day combat course (Gomez-Merino et al, 2005). In addition, testosterone was significantly decreased to clearly hypogonadal levels in young male soldiers after 8 weeks of extremely stressful training (Bernton et al, 1995).…”

Improved Sleep Quality is Associated with Reductions in Depression and PTSD Arousal Symptoms and Increases in IGF-1 Concentrations

“…10,11 In military personnel, the stress of combat training (i.e., deficiencies in sleep, energy, and water) significantly reduced plasma BDNF and IGF-1, which resumed to baseline levels following the cessation of training. 12,13 This finding illustrates the relationship between chronic stress and the restoration of physiological equilibrium upon stressor elimination. Evidence also suggests that the BDNF/IGF-1 system contributes to sleep homeostasis, including the regulation of restorative slow wave sleep oscillations.…”