Associations between salivary alpha-amylase and catecholamines--a multilevel modeling approach.

Salivary alpha-amylase (sAA) serves as indicator for sympathetic activity. However, previous findings on the association between aggregated sAA and other sympathetic markers, namely norepinephrine and epinephrine, were mixed. We therefore assumed that time-sensitive statistical analyses might help identifying possible associations of sAA and catecholamines. Data from two studies were analyzed. In Study 1, 13 men were examined in a randomized repeated within-subjects double-blind study with yohimbine/placebo. In Study 2, 30 men were randomized in a repeated within-subjects design to psychosocial stress/rest. Associations of repeatedly assessed sAA, norepinephrine, and epinephrine in blood were analyzed using multilevel modeling. Over the time course, sAA was significantly associated with the catecholamines (Study 1: R(2)=.43, Study 2: R(2)=.09) and both served as mediators of sAA increases. Additional exploratory analyses suggest stronger associations during challenge/stress than during placebo/rest. These findings further support sAA as marker of sympathetic activity.