Stressful life events are associated with low secretion rates of immunoglobulin A in saliva in the middle-aged and elderly

Whether chronic stress experience is related to downregulation of secretory immunoglobulin A (S-IgA) was tested in two substantial cohorts, one middle aged (N = 640) and another elderly (N = 582), comprising similar numbers of men (N = 556) and women (N = 666) and manual (N = 606) and non-manual (N = 602) workers. Participants indicated from a list of major stressful life events, up to six, they had experienced in the past 2 years. They also rated how disruptive and stressful the events were, at the time and now, as well as their perceived seriousness; the products of these impact values and event frequency were adopted as measures of stress load. From unstimulated 2-min saliva samples, saliva volume and S-IgA concentration were measured, and S-IgA secretion rate determined as their product. There was a negative association between the stress load measures and the S-IgA secretion rate, still evident following adjustment for such variables as smoking and saliva volume. The associations also withstood adjustment for sex, cohort, and household occupational status. Although these associations are small in terms of the amount of variance explained, they nonetheless suggest that chronic stress experience either decreases IgA production by the local plasma cells or reduces the efficiency with which S-IgA is transported from the glandular interstitium into saliva. Given the importance of S-IgA in immune defence at mucosal surfaces and the frequency with which infections are initiated at these surfaces, S-IgA downregulation could be a means by which chronic stress increases susceptibility to upper respiratory tract infection.