Change in sickness behavior assessed with the Sickness Questionnaire after endotoxin challenge is associated with the degree of change in inflammatory cytokines

The Sickness Questionnaire is a newly developed questionnaire for self-reported sickness behavior in humans. Here, we determined the time-course of sickness behavior and the association with changes in cytokine levels in an experimental study where 22 subjects received 2.0 ng/kg endotoxin or placebo in a crossover design, with a minimum of 20 days between injections. The Sickness questionnaire (from 0 to 30) and cytokines interleukin (IL)-6, IL-8 and tumor necrosis factor (TNF)-alpha were assessed at five time points: baseline, 1.5 h, 3 h, 5 h and 7 h post injection. Sickness behavior after endotoxin injection peaked at 1.5 and 3 h (Sickness Questionnaire score 18.9 and 19.8, respectively, vs baseline 5.8, p’s