Self-reported sleep duration, white blood cell counts and cytokine profiles in European adolescents: the HELENA study

• Morning immune markers and sleep duration were studied in European adolescents.
• Morning cortisol levels were higher with shorter sleep duration.
• Morning counts of white blood cells and T-cells were higher with shorter sleep.
• Sleeping between 8 and 9 h/night was associated with higher morning IL-4 levels.
• Sleeping ≤8 or ≥9 h/night was associated with more pro-inflammatory profiles.

BackgroundSleep patterns face important changes during adolescence. This can have implications for the immune system, which is regulated by the sleep–wake cycle; however, most studies relating sleep and immune system have been conducted on adults.ObjectiveTo study the relationships between sleep duration, immune cell counts, and cytokines in European adolescents participating in the HELENA Cross-Sectional Study.MethodsAdolescents (12.5–17.5 years; n = 933; 53.9% girls) were grouped according to self-reported sleep duration into <8, 8–8.9 and ≥9 h/night. Blood samples were collected in the morning after an overnight fast to analyze counts of white blood cells (WBC), neutrophils, lymphocytes, monocytes, eosinophils, basophils, the lymphocyte subsets CD3+, CD4+, CD8+, CD45RA+, CD45RO+, CD3−CD16+56+ and CD19+, and concentrations of cortisol, CRP, IL-1, IL-2, IL-4, IL-5, IL-6, IL-10, TNF-α and IFN-γ. Pro-/anti-inflammatory and Th1/Th2 cytokine ratios were calculated. Immune parameters were correlated to sleep duration and compared between the three groups.ResultsSleep duration was negatively associated with cortisol levels and WBC, neutrophil, monocyte, CD4+ and CD4+CD45RO+ counts; in girls it is also negatively associated with IL-5 and IL-6 levels. The 8–8.9 h/night group presented the highest IL-4 values and the lowest pro-/anti-inflammatory and Th1/Th2 cytokine ratios.ConclusionA sleep duration of 8–8.9 h/night was associated with a healthier immune profile in our adolescents.