Stress-induced changes in human salivary alpha-amylase activity -- associations with adrenergic activity

The salivary enzyme alpha-amylase has been proposed to indicate stress-reactive bodily changes. A previous study by the authors revealed marked increases in salivary alpha-amylase following psychosocial stress, indicating a stress-dependent activation of salivary alpha-amylase. Salivary alpha-amylase has been suggested to reflect catecholaminergic reactivity. Our aim was to assess/evaluate a possible relationship between salivary alpha-amylase and adrenergic parameters, i.e. catecholamines, as well as other stress markers. Using an intra-individual repeated measures design, 30 healthy young men underwent the Trier Social Stress Test (TSST), which consists of a mental arithmetic task and free speech in front of an audience and a control condition in randomized order. Salivary alpha-amylase and salivary cortisol as well as plasma catecholamines and cardiovascular activity were repeatedly measured before, during, and after both conditions. Significant differences were found between the stress and the rest condition in salivary alpha-amylase, salivary cortisol, plasma catecholamines, and cardiovascular parameters (heart rate, LF, HF, LF/HF). However, general alpha-amylase responses (area under the curve) were not associated with general responses in catecholamines and cortisol in the stress condition (r smaller than 0.25 for all analyses). Analysis of cardiovascular parameters indicates a positive relationship between amylase and sympathetic tone (LF/HF) during stress. Salivary alpha-amylase is sensitive to psychosocial stress. Since it does not seem to be closely related to other biological stress markers such as catecholamines and cortisol, salivary alpha-amylase may be a useful additional parameter for the measurement of stress.