Stress-induced increases in salivary alpha-amylase levels were correlated with increases in amylase output but not with saliva flow rate, indicating flow rate is not a confounder.
Does the Trier Social Stress Test induce changes in salivary alpha-amylase independent of saliva flow rate in human subjects?
Salivary alpha-amylase can be validly measured using salivettes without needing to assess saliva flow rate, as stress-induced increases are independent of flow rate.
The stress response of salivary alpha-amylase (sAA) has been suggested as an index for sympathetic nervous system activation. However, concurrent inhibition of the parasympathetic nervous system is discussed as a confounder due to suppression of saliva flow rate. Here we set out to test the influence of stress-induced changes in flow rate on sAA secretion. Twenty-six subjects underwent the Trier Social Stress Test and a control condition. Saliva was sampled by passive drooling or salivettes. Saliva flow rate, sAA levels and output, salivary cortisol, and heart rate variability were measured. Flow rate increased only when sampled by passive drooling. Stress-induced increases in amylase levels were correlated with increases of amylase output but not with flow rate. Results indicate that flow rate is not a confounder of stress-induced sAA activation and suggest that valid measurements of sAA can be obtained by salivettes without the need for assessment of flow rate.
Rohleder et al. (2006) studied this question. Trier Social Stress Test vs. Control condition was evaluated on Influence of stress-induced changes in flow rate on salivary alpha-amylase (sAA) secretion. Stress-induced increases in salivary alpha-amylase levels were correlated with increases in amylase output but not with saliva flow rate, indicating flow rate is not a confounder.