title: Salivary IgA as a risk factor for upper respiratory infections in elite professional athletes.
abstract: The relationship between physiological and psychological stress and immune function is widely recognized; however, there is little evidence to confirm a direct link between depressed immune function and incidence of illness in athletes.
  
  
  OBJECTIVE
  To examine the relationship between salivary immunoglobulin A (s-IgA) and upper respiratory infections (URI) in a cohort of professional athletes over a prolonged period.
  
  
  METHODS
  Thirty-eight elite America's Cup yacht racing athletes were studied over 50 wk of training. Resting, unstimulated saliva samples were collected weekly (38 h after exercise, consistent time of day, fasted) together with clinically confirmed URI, training load, and perceived fatigue rating.
  
  
  RESULTS
  s-IgA was highly variable within (coefficients of variation [CV] = 48%) and between subjects (CV = 71%). No significant correlation was found between absolute s-IgA concentration and the incidence of URI among athletes (r = 0.11). However, a significant (28%, P < 0.005) reduction in s-IgA occurred during the 3 wk before URI episodes and returned to baseline by 2 wk after a URI. When an athlete did not have, or was not recovering from URI, a s-IgA value lower than 40% of their mean healthy s-IgA concentration indicated a one in two chance of contracting an URI within 3 wk.
  
  
  CONCLUSIONS
  On a group basis, relative s-IgA determined a substantial proportion of the variability in weekly URI incidence. The typical decline in an individual's relative s-IgA over the 3 wk before a URI appears to precede and contribute to URI risk, with the magnitude of the decrease related to the risk of URI, independent of the absolute s-IgA concentration. These findings have important implications for athletes and coaches in identifying periods of high URI risk.
authors.affiliation: School of Sport and Exercise Sciences, Loughborough University, Loughborough, UNITED KINGDOM. vernon.neville@gmail.com
authors.forename: Vernon
authors.initials: V
authors.lastname: Neville
authors.forename: Michael
authors.initials: M
authors.lastname: Gleeson
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Folland
mesh_terms: D000064:Acclimatization; D000223:Adaptation, Psychological; D000328:Adult; D015331:Cohort Studies; D017079:Exercise Tolerance; D006305:Health Status Indicators; D006801:Humans; D007071:Immunoglobulin A, Secretory / Q000032:analysis*; D015994:Incidence; D008297:Male; D018763:Muscle Fatigue / Q000276:immunology; D011446:Prospective Studies; D012141:Respiratory Tract Infections / Q000453:epidemiology* / Q000209:etiology / Q000276:immunology; D012307:Risk Factors; D012463:Saliva / Q000276:immunology*; D012767:Ships; D013177:Sports / Q000502:physiology*; D013223:Statistics as Topic; D013312:Stress, Physiological / Q000276:immunology; D011795:Surveys and Questionnaires; D016526:Workload
chemical_list: D007071:Immunoglobulin A, Secretory