Abstract / Description
BackgroundWearable monitoring of sedentary behavior is increasingly used in digital cardiovascular care, but the validity of consumer-grade wrist-worn trackers in older patients with cardiac issues is unclear.ObjectiveThis study aimed to evaluate the agreement between sedentary time measured by a consumer-grade wrist-worn tracker (Fitbit Inspire 3; Fitbit LLC) and a research-grade waist-worn accelerometer (ActiveStyle Pro HJA-750C; Omron Healthcare Co, Ltd) used as the comparator, in Japanese outpatients with cardiac issues under free-living conditions.MethodsFifty-one outpatients with heart failure (28/51, 55%) or ischemic heart disease (23/51, 45%; mean age 78.4, SD 9.0 years; 25/51, 49% male) simultaneously wore both devices for 7 consecutive days. Sedentary time was assessed within a standardized 12-hour daytime window (9 AM to 9 PM) at 1-minute epochs. Agreement was examined using Pearson correlation, Bland-Altman analysis (after confirming normality of the paired differences), Lin concordance correlation coefficient (CCC), and Cohen kappa for distribution-based tertile classification. A constant bias correction was applied, with leave-one-out cross-validation (LOOCV) used as an internal-consistency check on the stability of the sample mean bias. Moderators of the bias were explored using multivariable regression.ResultsMean sedentary time within the 12-hour window was 497.9 (SD 86.5) minutes for the comparator and 559.9 (SD 84.3) minutes for the Fitbit. The devices were strongly correlated (r=0.905, 95% CI 0.838-0.945; P