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.
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.
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.
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.
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.
School of Sport and Exercise Sciences, Loughborough University, Loughborough, UNITED KINGDOM
Address for correspondence: Vernon Neville, 5 Castledine St Extension, Loughborough, LE11 2NT, United Kingdom; E-mail: firstname.lastname@example.org.
Submitted for publication December 2007.
Accepted for publication February 2008.