Objective: The influence of physical activity and diurnal variation during 24-hour ambulatory blood pressure monitoring (ABPM) has been well demonstrated. We prospectively evaluated the usefulness of electronic activity monitoring for the actual physical activity and diurnal variation of ABPM in hypertensive patients at real-world practice. Methods: 24-hour ABPM(Spacelabs 90207,USA) with an electronic activity monitor(SenseWear PRO2,USA) was performed on 10 normotensive volunteers for validation, and then performed on 73 hypertensive patients (M:F=44:29, Age:47±13 year-old) who were initially diagnosed at the clinic for usefulness of activity monitoring. To interpret the ABPM results of 73 hypertensive patients, we obtained the actual awake/sleep periods of every patient with using an electronic activity monitor and the daytime(06:00-22:00)/night time(22:00-06:00) periods by arbitrary method. Results: The activity values from the 10 normotensive volunteers were obtained according to 4 activities: sleeping, sitting, walking and running. The values agreed with the activities, and well correlated with blood pressure(BP) and heart rate. Out of 73 patients who were initially diagnosed hypertension, 15 patients turned out normotension after APBM. By arbitrary method, 58 hypertensives were classified with 19 non-dippers, 36 dippers, 1 extreme dipper and 2 reverse dippers. The nocturnal mean BP derived by the actual period was significantly lower than that derived by the arbitrary period (121.7±12.3/77.3±10.7 vs 117.4±11.3/74.1±10.3mmHg, p<0.00). The nocturnal BP fall derived by the actual period was significantly larger than that by the arbitrary period (13.1±8.0/9.9±5.9 vs 18.3±7.7/13.9±5.5mmHg, p<0.00). Twelve among the 19 non-dippers determined by the arbitrary period were re-classified as dippers when the actual period was used. One among the 58 hypertensives, as determined by the arbitrary period, was also re-classified as a non-hypertensive. Conclusion: The electronic activity monitor was valuable method to determine the actual activity level at real-world practice. These results suggest that the accuracy and reproducibility of the 24-hour ABPM will be improved by using an electronic activity monitor
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