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In Japan, forest-air bathing and walking (shinrin-yoku) has been proposed as a health-facilitating activity in which people spend a short period of time in a forest environment. Initially, we examined the usefulness of salivary amylase activity as an indicator of an individual's stress levels in a forest environment. The circadian rhythm of salivary amylase activity was measured in healthy young male subjects under stress-free conditions. The salivary amylase activity remained relatively constant throughout the day. Salivary amylase activity was then measured before and after walking in both urban and forest environments using a hand-held monitor. Our results indicated that (i) the circadian rhythm fluctuations in salivary amylase activity were much smaller than the stressor-induced variations; (ii) salivary amylase activity was an excellent indicator of the changes in sympathetic nervous activity; and (iii) the forest was a good environment in which people could experience much less environment-derived stress.

It is considered that measurement of salivary alpha-amylase activity is a useful tool for evaluating the sympathetic nervous system. The purpose of this research is to demonstrate a new design of a flat-chip microanalytical enzyme sensor (flat-chip sensor) for salivary amylase activity as a Micro-Electro-Mechanical Systems (MEMS), which may be used for wearable analytical systems. To meet this purpose, the biosensor needs to be miniaturized and to possess high-sensitivity. A pre-column and a flat-enzyme electrode were incorporated in a flow cell of volume 25.7 ml. In order to miniaturize the flow cell, two enzymatic membranes containing maltose phosphorylase obtained from Enterococcus hirae (MP membrane) and glucose oxidase and peroxidase (GOD-POD membrane) were immobilised on the same planar surface. As a result, a flat-chip sensor incorporating a flow cell as small as a C battery was produced. The optimum conditions of three parameters of the fabricated flat-chip sensor, the immobilising method of the enzymatic membrane, dropping volume of the mixed enzymatic solution and flow rate of the sample solution, were examined. An analytical system for 0-190 kU/l amylase activity with R(2) of 0.97 was fabricated with a sample volume of 50 microl. This research indicates the possibility of a wearable biosensor for continuous monitoring of salivary amylase activity.

This study evaluated a novel non-verbal communication method for people with severe motor and intellectual disabilities (SMID) based on a biochemical marker, salivary amylase. The physical and psychological status of 10 people with SMID was quantitatively evaluated using a hand-held salivary amylase activity monitor. Each patient needed daily gastric and/or bronchial tube exchanges and these medical procedures were thought to cause severe distress and pain. Salivary amylase activity and heart rate were simultaneously measured during 32 medical procedures. The medical procedures resulted in a significant mean increase for individuals of 70% in salivary amylase activity. The increase in salivary amylase activity was more than four-fold that observed for heart rate. The structural equation modelling analysis also demonstrated a significant correlation between pain and salivary amylase activity. Our data indicate that salivary amylase activity might be used as a non-verbal method of assessing pain in people with SMID.

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