Biological Markers and Salivary Cortisol

This chapter focuses on salivary cortisol in relation to biological markers. Specifically, associations with conventional cardiovascular risk factors and metabolic abnormalities (body mass index, waist circumference, waist/hip ratio, lipid status, glucose, blood pressure, heart rate and heart rate variability), markers related to inflammation (C-reactive protein, cytokines and tumor necrosis factor-alpha) and other stress hormones (adrenaline and noradrenaline) were studied. The focus was on healthy adult populations; studies on patient populations and pregnant women were excluded. Studies on genome variations and pharmacological interventions were also excluded. After meeting all exclusion criteria, 42 papers remained. In total, 273 associations between salivary cortisol and any of the markers mentioned were studied, comprising 241 associations on metabolic abnormalities, 30 on inflammation, and 2 on stress hormones. Of the salivary cortisol measures reported for evaluations of all markers tested were 136 (49%) single time points, 100 (37%) deviations, 36 (13%) AUC, and 1 (1%) dexamethasone test. Of these, 72 (26%) were statistically significant, and 201 (74%) indicated non-significant findings.Several of the markers tested showed low or no association with any of the measurements of salivary cortisol. The number of studies exploring the association between cortisol in saliva and markers for inflammation is low, which limits the possibility of interpretation. The number of studies on adrenaline and noradrenaline is also low. To sum up, the proportion of non-significant findings was considerable. This may be due to a large number of studies with relatively small study populations. This is true for metabolic abnormalities, markers related to inflammation as well as other stress hormones. Further studies on inflammatory markers and approaches designed to study variability in other systems in relation to cortisol variability are required.

Keywords: Salivary cortisol, body mass index, waist circumference, waist/hip ratio, lipid status, glucose, blood pressure, heart rate, C-reactive protein, cytokines, adrenaline, noradrenaline.