Combat-training stress in soldiers increases S100B, a marker of increased blood-brain-barrier permeability, and induces immune activation.

BACKGROUND: Experimental data suggest stress-related cognitive dysfunction may be associated with increased blood-brain-barrier (BBB) permeability secondary to immune activation.

METHODS: We investigated the relationship between prolonged and intense physical and psychological combat-training stress, immune activation and blood-brain-barrier permeability in 37 healthy male army medical rapid response troops.

RESULTS: Soldiers during intense combat training showed greater self-reported stress, anxiety and depression levels than at rest, as assessed by specific questionnaires. S100B, a marker of BBB permeability, as well as serum cortisol, IL-6 and TNF-α concentrations, were significantly increased in soldiers during combat training compared to rest (all p<0.05). Serum S100B correlated negatively with morning serum cortisol in soldiers during combat training, but not during the rest period (r=-0.387, p<0.05).

CONCLUSION: We conclude that combat training inducing significant levels of stress, depression and anxiety is accompanied by evidence of increased blood-brain barrier permeability and by increases in systemic pro-inflammatory mediators.