The inflammatory immune system after wake up in healthy male individuals: A highly standardized and controlled study

This study investigates the effects of two light conditions on innate proinflammatory IL-6 cytokines and the cortisol awakening response. The between-subject experiment was conducted with 55 healthy adult-males (aged M _bright = 24.40, SD = 4.58; M _dim = 25.47, SD = 4.96) in a standardized sleep laboratory setting with 60-min light exposure post-awakening. Cortisol significantly increased with bright light exposure as compared to dim light (significant interaction effect). As for IL-6, the main effects of time and light condition were significant, however, the interaction effect between light and time was insignificant. Results replicate stimulatory effects of bright light on cortisol. In general, IL-6 concentrations decreased in both light conditions; however, bright light graphically showed higher concentrations 45-90 min after exposure in comparison to dim light, thus bright light has a potential stimulatory effect on IL-6 production.