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

Background: Sleep 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. Objective: To study the relationships between sleep duration, immune cell counts, and cytokines in European adolescents participating in the HELENA Cross-Sectional Study. Methods: Adolescents (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-alpha and IFN-gamma. Pro-/anti-inflammatory and Th1/Th2 cytokine ratios were calculated. Immune parameters were correlated to sleep duration and compared between the three groups. Results: Sleep 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. Conclusion: A sleep duration of 8-8.9 h/night was associated with a healthier immune profile in our adolescents. (C) 2014 Elsevier B. V. All rights reserved.