Objective: The purpose of this study was to compare the performance of the salivary cortisol immunoassay kits that were manufactured by DRG International, Inc., Salimetrics, LLC., and IBL Hamburg, which were widely used in neuroendocrine research. Correlations between plasma and salivary cortisol concentrations and between enzyme-linked immunosorbent assay (ELISA) and luminescence immunoassay (LIA) were investigated.
Methods: Saliva and plasma samples were collected in eight participants who took part in the study of the exercise stress testing. In total, forty salivary cortisol samples were assayed by means of the three salivary cortisol immunoassay kits. Plasma cortisol concentrations were determined by ELISA kit (IBL).
Results: Salivary cortisol concentrations measured by the three immunoassay kits were significantly and highly correlated with plasma cortisol concentrations (r ≥ .863). Scattergrams also indicated that exponential curve well explained the relationship between salivary and plasma cortisol concentrations (r ≥ .925). Salivary cortisol concentrations measured by LIA (IBL) was correlated with salivary cortisol concentrations measured by ELISA (DRG and Salimetrics: r=.943 and .985, respectively). Values of cortisol concentration measured by ELISA (DRG) were higher than those by ELISA (Salimetrics) and LIA (IBL).
Conclusion: Salivary cortisol concentrations that were measured by the three immunoassay kits reflected the variations of plasma cortisol concentration. Differences in immunoassay methods (ELISA and LIA) did not influence the values of cortisol concentration. These findings indicated that it is possible to assess stress by measuring salivary cortisol without the need for blood sampling.

An objective assessment of stress is needed to manage stress and prevent the development of stress-related diseases such as depression and coronary heart disease. In this paper, we discussed the possibility of applying saliva to an assessment of stress. We illustrated the procedures for collecting and analyzing saliva, and reviewed the relationships of acute, chronic, psychological, or physical stress to seven salivary substances: Cortisol, Dehydroepiandrosterone, Testosterone, Chromogranin A, 3-Methoxy-4-hydroxyphenyglycol, α-Amylase, and Secretory Immunoglobulin A. Considering unique characteristics of each salivary substance and purposes of the study or the non-invasive assessment, salivary substances should be selected for the assessment of stress.

Previous studies among middle-aged and older adults have shown that engagement in exercise with others is more strongly associated with better mental health than engagement in exercise alone. However, the applicability of such findings to workers remains unclear. This study aimed to examine whether 1) engagement in exercise with others and time spent exercising with others were associated with lower stress response and mental distress among workers, and 2) self-determined motivation toward exercise mediated these associations among workers. This was a cross-sectional study. A web-based questionnaire survey was conducted among 810 workers aged 20 to 59 years. The survey measured respondents’ engagement and time spent exercising alone and with others, self-determined motivation toward exercise, psychological and physical stress responses, mental distress, and basic factors. Basic factors were treated as covariates. The analyses of covariance showed that engagement in exercise with others was significantly associated with lower psychological and physical stress responses and mental distress, while engagement in exercise alone was not. Multiple regression analyses revealed that longer time spent exercising with others was not associated with lower psychological and physical stress responses or mental distress. Path analyses showed that mediation effect of self-determined motivation on these associations was not significant. Although dose-response associations and the mediating role of self-determined motivation were not confirmed, this study found that engagement in exercise with others was associated with lower stress responses and mental distress among workers.