Household illness is the strongest predictor of upper respiratory tract symptom risk in elite rugby union players

J Sci Med Sport. 2021 May;24(5):430-434. doi: 10.1016/j.jsams.2020.10.011. Epub 2020 Oct 24.


Objectives: To identify periods of increased risk for upper respiratory tract symptom (URTS) episodes, and examine whether biomarkers and/or self-reported lifestyle and wellness data can predict URTS risk in elite rugby union players.

Design: Prospective, longitudinal and repeated-measures study.

Methods: Salivary secretory immunoglobulin A (SIgA), salivary cortisol, URTS, internal training load and self-reported lifestyle and wellness data including household illness, stress, mood, fatigue, muscle soreness and sleep quality were repeatedly measured in elite Southern hemisphere rugby union players (n=28) throughout a season. Univariate frailty model analysis, which included 495 observations, was used to determine predictors of URTS risk.

Results: Surprisingly, the highest incidence of URTS occurred after rest weeks, namely the Christmas break and bye weeks (i.e., no scheduled trainings or matches); whereas URTS risk was reduced during weeks involving international travel (Hazard ratio (HR): 0.43, p<0.001)). Household illness was the strongest predictor of URTS risk; players were almost three-fold more at risk for an URTS episode when illness in the household was present (HR: 2.90, p=0.002). A non-significant, but potentially important trend for an inverse association between SIgA concentration and URTS incidence was also observed (HR: 0.99, p=0.070).

Conclusions: Rest weeks were identified as periods of increased risk for URTS; while international travel did not appear to increase players risk for URTS. Incidence of household illness and SIgA concentration independently predicted URTS risk, with household illness being the strongest predictor. These findings can assist practitioners monitoring and management of athletes to potentially reduce URTS risk.

Keywords: Athlete; Competition; Immunity; Training; Travel.

MeSH terms

  • Adult
  • Biomarkers / metabolism
  • Disease Transmission, Infectious*
  • Family Characteristics*
  • Family*
  • Football*
  • Humans
  • Hydrocortisone / metabolism
  • Immunoglobulin A, Secretory / metabolism
  • Longitudinal Studies
  • Prospective Studies
  • Respiratory Tract Infections / transmission*
  • Saliva
  • Surveys and Questionnaires
  • Young Adult


  • Biomarkers
  • Immunoglobulin A, Secretory
  • Hydrocortisone