The association between interleukin-6, sleep, and demographic characteristics.

We examined the relationship between the pro-inflammatory cytokine IL-6 and sleep architecture in 70 healthy men and women. Blood was drawn in the early morning for assessment of IL-6 followed by nocturnal sleep monitoring with polysomnography. Sleep records were scored for sleep stages using standard criteria. Morning IL-6 levels were positively correlated with REM latency after sleep onset [rho = .31, p = .01], percent (%) stage 1 sleep [rho = .23, p = .053], % wake after sleep onset (WASO) [rho = .29, p<.05]. IL-6 levels were negatively correlated with sleep efficiency [rho = -.36, p<.01] and slow wave sleep (SWS) [rho = -.26, p<.05]. After controlling for demographic variables including race, gender, age, and BMI, multiple hierarchical regression analyses revealed that morning IL-6 levels accounted for a significant portion of the variance of REM latency (p<.01), sleep efficiency (p<.01), and % WASO (p = .01). IL-6 was no longer associated with % stage 1 sleep, SWS, and total sleep time after controlling for the demographic characteristics. These findings suggest that the inflammatory marker IL-6 is associated with sleep quality and that certain individual characteristics such as race, gender, and age modify that relationship. Higher IL-6 levels were associated with lower quality of sleep among healthy asymptomatic men and women.