Saliva pH as a biomarker of exam stress and a predictor of exam performance

Background: Salivary pH is regulated by the sympathetic and parasympathetic nervous system; therefore, it may serve as a biomarker of stress. Aims: To assess the associations between the cognitive and emotional dimensions of exam stress and pH levels, and the predictability of salivary pH in relation to test performance. Methods: A prospective study. Eighty-three nursing students answered a questionnaire on stress appraisals, experienced stress, test anxiety (including worry and emotionality subscales) and health behaviors, and gave a saliva sample for measuring pH on the morning of their first term exam and three months later. Their performance on the test (grades) was also recorded. Results: Levels of pH in saliva were higher (levels of acidity were lower) in the post exam compared to the exam period, in parallel to lower threat appraisal, experienced stress, and test anxiety levels post exam. Controlling for smoking, physical activity and working hours per week, pH levels at both time points were predicted by appraised threat regarding the exam situation, experienced stress, and the emotionality dimension of test anxiety. pH at Time 1 predicted performance on the exams and mediated the associations of experienced stress and emotionality subscale with test performance. Conclusions: the present study indicates that pH levels may serve as a reliable, accessible and inexpensive means by which to assess the degree of physiological reactions to exams and other naturalistic stressors.