Salivary Biomarkers (Opiorphin, Cortisol, Amylase, and IgA) Related to Age, Sex, and Stress Perception in a Prospective Cohort of Healthy Schoolchildren

Abstract

Background: The use of easily accessible biomarkers for assessing young patients' health is weighty. This cohort study is aimed at measuring stress/immune biomarkers in the saliva of healthy school-age children and comparing subgroups according to age, sex, and stress perception. Material and Methods. 503 children under 12 years old (8.7 ± 1.3) were included with anthropometric evaluation (height, waist, hip circumference, body weight, and body mass index (BMI)). Levels of opiorphin (OPI), free cortisol, alpha-amylase (sAA), and secreted immunoglobulin (sIgA) were determined by quantitative assays (ELISA) in unstimulated saliva. Unpaired t-test, Welch test, and Mann-Whitney U test were applied for appropriate group comparisons, and the correlation between variables was analyzed with Spearman's rank coefficient. Results were considered significant at p < 0.05.

Results: sIgA and sAA exhibited significant differences depending on age and sex: IgA (ng/mL): 86 ± 68.6 vs. 104.9 ± 72.1 for (6-7 y.o.) and (8-11 y.o.), respectively, and 108.1 ± 80.1 vs. 94.6 ± 62.2 for male and females, respectively; sAA (U/mL): 78.9 ± 54.4 vs. 100.5 ± 81.2 for (6-7 y.o.) and (8-11 y.o.). No difference related to age or sex between groups was observed for cortisol and OPI. However, OPI levels were higher and correlated to prior stress exposure in children (0.31 ± 0.4 vs. 0.26 ± 0.5 ng/mL, p = 0.031). sAA was negatively correlated to low mood self-declaration in children in the last two weeks (r = -0.10, p = 0.045).

Conclusions: sIgA and sAA can be used as sex- and age-related biomarkers in children 6-12 y.o., which is not the case for free cortisol and opiorphin. However, OPI reflected previous exposure to stress, suggesting its use for evaluating stress-related changes in children.

Figure 1

Study flowchart.

Figure 2

Anthropometric parameters according to (a) sex, (b) age group, (c) age group and sex, and (d) prior stress events (SE0 vs. SE1). One bar graph for each comparison (four graphs in total). Mean ± standard deviation and p value with statistical difference marked in values. n: number of examined children; ns: not significant value in statistical analysis; sIgA: salivary IgA; sAA: salivary alpha-amylase; OPI: opiorphin; SE1: group of children with stressful experience in the past; SE0: group of children without stressful experience in the past.

Figure 3

Salivary parameters according to (a) sex, (b) age group, (c) age group and sex, and (d) prior stress events (SE0 vs. SE1). One bar graph for each comparison (four graphs in total). Mean ± standard deviation and p value with statistical difference marked in values. n: number of examined children; ns: not significant value in statistical analysis; sIgA: salivary IgA; sAA: salivary alpha-amylase; OPI: opiorphin; SE1: group of children with stressful experience in the past; SE0: group of children without stressful experience in the past.

Figure 4

Comparison of salivary opiorphin (mean ± standard deviation). SE0: children free of stressful experiences in the past; SE1: children with stressful experiences in the past. Children from the SE1 group showed higher salivary concentration of this peptide. p value with statistical correlation, p < 0.05.