Cytokine concentrations in saliva vs. plasma at rest and in response to intense exercise in adolescent athletes.

Background: Salivary measures are advantageous in conducting large paediatric studies involving repeated measures. However, research measuring salivary cytokines in youth is limited.

Aim: Compare salivary with plasma concentrations of inflammatory cytokines at rest and following exercise in adolescent swimmers (21 male, 22 female).

Methods: Following collection of resting saliva and blood samples, participants performed a bout of high-intensity interval swimming, with samples taken again ∼15 min post-swimming and analysed for interleukin-6 (IL-6), interleukin 10 (IL-10), and tumour necrosis factor-alpha (TNF-α).

Results: Resting IL-10 was significantly lower, while IL-6 and TNF-α were significantly higher in saliva compared with plasma. IL-10 increased from pre- to post-swimming in plasma, but less so in saliva (51% vs. 29%;  = 0.02). TNF-α decreased post-swimming in saliva, but not in plasma (-27% vs -1%;  = 0.01). IL-6 decreased post-swimming in saliva compared with plasma (-21% vs. -3%;  0.06). Intraclass correlation coefficients (ICC) revealed no association between salivary and plasma IL-6 and TNF-α, while IL-10 showed a weak correlation only at rest (ICC = 0.39;  = 0.05).

Conclusions: Differences in concentrations and exercise responses, along with weak correlations, suggest that salivary cytokine levels are not an accurate representation of blood cytokine levels, and should not be used as a surrogate measure in paediatric studies.