Three Days of ActiGraph® Use Are Sufficient to Determine the Time Spent in Sedentary Behavior, and in Moderate and Moderate-to-Vigorous Physical Activity, in People with Major Depressive Disorder

Modifications to daily sedentary behavior (SB) and participation in moderate-to-vigorous physical activity (MVPA) may provide beneficial results in the prevention and management of mental disorders, such as Major Depressive Disorder (MDD). This cross-sectional research investigated the minimum number of follow-up days needed to reliably estimate the time spent in SB and MVPA from accelerometer data in people with MDD. SB and physical activity (PA) were assessed using an accelerometer, and classified as time spent in SB and in different PA intensities (light—LPA, moderate—MPA, vigorous—VPA, MVPA, or total—TPA). The minimum days of use were calculated using Spearman–Brown analyses, considering only variables with an ICC > 0.8 (cut point-considered acceptable). In the results, 98 people with MDD showed no differences between the days of the week, and an ICC > 0.8 for SB, MPA, and MVPA (for 2-3-4-5-6 vs. 7). Thus, Spearman–Brown analyses were performed considering 2 days (minimum days with ICC > 0.8) and 7 days (maximum days of original test with ICC > 0.8). Our results suggest that a minimum of 3 days of accelerometer use is necessary to reliably estimate the time of SB, MPA, and MVPA. This finding has a significant practical application, allowing data collection using a reduced duration of accelerometer wear. The optimization of time needed in this context permits the utilization of accelerometers among a greater number of individuals, possibly affecting the sample size of MDD patients in research and decreasing acquisition costs in this scientific area.