Salivary alpha-amylase activity and salivary flow rate in young adults

Abstract

The secretion of salivary alpha-amylase (sAA) is more associated with psychoneuroendocrinological response to stress than with the flow rate and age. The aim of this cross sectional study is to build an explanatory model based on patterns of relationship between age 20-39 in resting and stimulated saliva under no stressful condition in healthy volunteers. Both resting and stimulated saliva were collected from 40 subjects. The sAA values were log-transformed, the normality assumption was verified with the Shapiro-Wilk test and the reliability of the measurements was estimated by the Pearsons' r correlation coefficient. The estimated model was based on the theory of the Linear Mixed Models. Significant mean changes were observed in flow rate and sAA activity between resting and stimulated saliva. The final model consists of two components, the first revealed a positive correlation between age and sAA while the second one revealed a negative correlation between the interaction of age × flow rate in its condition (resting or stimulated saliva), with sAA. Both flow rate and age influence sAA activity.

Keywords: Salivary flow rate; age.; salivary alpha-amylase.

Fig. (1)

Scatterplot of Dlog(flow rate) vs Dlog(sAA) showing the groups that emerged after the k-means cluster analysis on Dlog(flow rate).

Fig. (2)

Scatterplot of Dlog(flow rate) vs Dlog(sAA) showing the groups that emerged after the k-means cluster analysis on Dlog(sAA).

Fig. (3)

Scatterplot of log(age) vs. Dlog(flow rate), showing subjects with decreased Dlog(sAA), r=0.51, N=16 (Dlog(sAA)<0.5).

Fig. (4)

Scatterplot of Dlog(flow rate) vs Dlog(sAA), showing subjects with decreased Dlog(flow rate), r=0.41 N=25 (Dlog(flow rate)<2.1).

Fig. (5)

Normal QQ-plot of the conditional residuals from the restricted (best) model.

Fig. (6)

Conditional predicted values vs conditional residuals of the restricted (best) model.