Measurement of Human Gastric Motility by Near-Infrared Light for the Assessment of Chronic Mental Stress

In this study, we focused on the relationship between mental stress and gastric motility and have tried to develop a measurement system of human gastric motility for the quantification of mental stress. A mental stress measurement system should be used easily in daily life. However, general measurement system as electrogastrography, endoscopy, CT, ultrasonic echogram isn´t suitable for the home use. Then, we have developed non-invasive and compact measurement system of gastric motility using near-infrared (NIR) light. This system consists of NIR LEDs and an avalanche photodiode (APD). APD receives the NIR light transmitting outside the body from NIR LEDs and reflecting on the gastric wall. In the experiment, an ultrasonic echogram was used simultaneously to confirm our new method. The result showed that the waveform got by our method coincides with the cycle of contractile activity of stomach, and it was proved that our measurement system using NIR light could measure gastric motility. In addition, we performed chronic mental stress measurement intended for students to examine relationship between chronic mental stress and gastric motility. Experimental period was from two weeks before graduation examination to two weeks after graduation examination. The result showed that chronic mental stress may invoke gastric dysrhythmia, and chronic mental stress could be evaluated by long term monitoring of gastric motility using our NIR measurement system