Social class, sex, and age differences in mucosal immunity in a large community sample

There have been very few reports addressing levels and distribution of commonly used PNI measures in large community samples. In this study, we report such data for secretion rates of secretory immunoglobulin A (sIgA), as determined from saliva samples taken from 1971 subjects interviewed as part of the West of Scotland Twenty-07 survey of health in West Central Scotland. Univariate analyses of demographic variables found lower sIgA and salivary flow to be significantly related to poorer social class, increased age, and being female. Smokers also had lower sIgA but not lower salivary flow. Multivariate analysis showed that demographic variables were significant predictors of sIgA independently of each other and assay variation. Adding smoking status to the equation confirmed it as an independent predictor and also indicated that social class differences in sIgA are partly explicable in terms of smoking status. In view of reported associations between sIgA levels and stress, its role as a first line of mucosal defense, and its relevance to health, these first results from a large survey are of interest. Further work is now needed to explore which factors, including psychosocial ones, may be contributing to subgroup differences.