Postoperative delirium, a common perioperative complication, is frequently observed in elderly surgical patients. Few studies have investigated the life rhythm of preoperative patients, and whether or not the preoperative life rhythm is associated with the development of postoperative delirium. The purpose of this study was to investigate the relationship between the preoperative circadian physical activity rhythm and postoperative delirium in cardiovascular surgery patients. A total of 43 patients who underwent cardiovascular surgery were included in this prospective study between July 2016 and September 2017 at Kobe University Hospital. All subjects used a "Life Microscope" wristband (a wristwatch-type terminal incorporating a 3-axis accelerometer monitoring) for 3-7 days at home before the planned surgery. Hourly mean values were calculated for the metabolic equivalents from the obtained activity amounts, and subsequently evaluated using cosine periodic regression analysis. The circadian rhythm parameters of mesor (24 h time series mean), amplitude (half the peak-trough variation), and acrophase (peak time) for the metabolic equivalents were obtained. The intensive care delirium screening checklist was used to assess for postoperative delirium. The acrophase significantly advanced in the postoperative delirium group (median, 11:55 h [interquartile range, 11:06-12:27 h]) compared to the group without postoperative delirium (median, 13:25 h [interquartile range, 12:52-14:13 h]) (p < .001). Furthermore, binary logistic regression analysis showed that advances in the physical activity phase remained independently associated with postoperative delirium (odds ratio, 0.003 [95% confidence interval, 0-0.63]). These results suggest that misalignment between advanced life rhythm before hospitalization and life rhythm after hospitalization might be associated with risk for developing postoperative delirium. Our results led us to speculate that adequate consideration of the patient's life rhythm before hospitalization is needed to prevent postoperative delirium.
Keywords: Postoperative delirium; circadian rhythm; cosine; periodic regression analysis; physical activity.