Circadian rhythm of preoperative period and effects of bright light on physiological activity

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Measurement of sleep-wake rhythm was carried out in the surgical patients by actigraphy.Mean sleep time (22:00 to 6:00) of 12 patients was following; 400 min at preoperative day 3(POD 3), 400min at POD 2 and 395 min at preoperative, 367 min at operative day, 307 min at post operative day 1 (POD 1), 284 min at POD2, 290 min at POD 3, 263 min at POD 4, and 282 min at POD 5.Bright light exposure during daytime increases parasympathetic nerve activity during the nighttime.A spectral analysis of heart rate was carried out on 11 young female adults in order to evaluate the effects of bright light exposure on autonomic nervous activity. Bright light was provided by fluorescent lamps during the daytime on day 1. Dim light was given on day 2. The average value during the sleep period was compared following diurnal exposure to bright or dim light. HF component was significantly greater from 23:30 h to 02:00 h after diumal exposure of bright light, being accompanied by lower heart rate during these periods. The results indicate that bright light exposure during the daytime could enhance parasympathetic activity around midnight.Effects of dim or bright-light exposure during the daytime on human gastrointestinal activity.We measured gastrointestinal activity using a breath hydrogen (indicative of carbohydrate malabsorption) and an electrogastrography (EGG, indicative of gastric myoelectric activity) test. Postprandial breath hydrogen excretion during the following nighttime period after daytime exposure to the dim-light condition was significantly higher than under the bright-light condition. The spectrum total power of the EGG recorded after taking the evening meal was significantly lower for the dim than bright-light condition. These results indicate that dim-light exposure during the daytime suppresses the digestion of the evening meal, resulting in malabsorption of dietary carbohydrates in it.