Table 2. Results for Fitbit charge HR.
Aggregate Data
(n = 87 340)
Data above ECG HR >116bpm
(n = 41 315)
Data below ECG HR <117bpm
(n = 46 025)
FB Mean HR, bpm (±SD) 108(29) 130(25) 89(15)
ECG Mean HR, bpm (±SD) 117(29) 142(19) 94(14)
Mean Absolute Difference, bpm (±SD) 11(16) 14(20) 8(9)
Mean Absolute Difference, % (±SD) 9.8 (14.0) 11.3 (17.0) 8.5 (10.4)
Correlation (r) .83* .58 * .73 *
Mean Bias, bpm (±SD) [95% CI] -9(17) [-9, -9] -13(21) [-13, -13] -5.3(11) [-5, -5]
95% Limits of Agreement (Upper, Lower) 24, -42 29, -54 16, -26
Standard Error of the Estimate (SEE) 16 20 10.0
*p < 0.0001FB = Fitbit Charge HR, SD= standard deviation, ECG= electrocardiograph, HR= heart rate, CI= confidence interval, n= per second ECG and FB data pairs.