Processing of Sedentary Time and Its Reference Equation in Patients with COPD

Sedentary time (ST) is associated with mortality independent of moderate-to-vigorous physical activity in patients with COPD. The proper processing methods for the measurement data and factors related to ST are still unknown. We investigated several conditions for determining the proper processing of ST accelerometric data and created a reference equation for ST using ST-related factors. In Study 1, we evaluated the minimum required number of days to obtain repeatability at different measurement times and assessed the effects of rainy days or weekend days on ST in patients with COPD. In Study 2, we detected the ST-related factors among 28 parameters and created a reference equation for ST using the detected factors. In Study 1, 38 patients with stable COPD were analyzed. The minimum number of days required for repeatability was 3 for 8-h wearing and 2 for 10-h wearing. The ST was significantly prolonged on rainy days, but not on weekends. In Study 2, 216 patients with stable COPD were analyzed. BMI, FEV1%pred, 6MWD, and mMRC were detected as ST-related factors, and a reference equation could be created using these four factors. The equation was validated for patients whose ST was ≥ 6 h. By using properly processed measurement data of ST, we created a reference equation for assessing ST that is expected to be useful for providing individual guidance on the shortening of ST to patients with COPD.