Accepted for/Published in: JMIR mHealth and uHealth
Date Submitted: Aug 9, 2018
Open Peer Review Period: Aug 13, 2018 - Sep 13, 2018
Date Accepted: Dec 9, 2018
(closed for review but you can still tweet)
Accuracy of Apple Watch Measurements of Heart Rate and Energy Expenditure in Patients with Cardiovascular Disease
ABSTRACT
Background:
Wrist-worn tracking devices such as the Apple Watch are becoming more and more integrated in healthcare. However, validation studies of these consumer devices remain scarce.
Objective:
This study aimed to determine the accuracy of the Apple Watch in measuring heart rate (HR) and estimating energy expenditure (EE) during a cardiopulmonary exercise test (CPET) in patients with cardiovascular disease.
Methods:
Forty patients (mean age 61.9 +/- 15.2 yrs, 80% male) with cardiovascular disease (70% ischemic, 22.5% valvular, 7.5% other) completed a graded maximal CPET on a cycle ergometer while wearing an Apple Watch. A 12-lead electrocardiogram (ECG) was used as criterion for HR, indirect calorimetry was used as criterion for EE. HR was analysed at three levels of intensity (seated rest, HR1; moderate intensity, HR2; maximal performance, HR3) for 30 seconds. The EE of the entire test was used. Bias or mean difference (MD), standard deviation of difference (SDD), limits of agreement (LoA) and intraclass correlation coefficients (ICCs) were calculated. Bland-Altman plots and scatterplots were constructed.
Results:
SDD for HR1, HR2 and HR3 was 12.4, 16.2 and 12.0 beats/min respectively. Bias and LoA (lower, upper LoA) were 3.61 (-20.74, 27.96) for HR1, 0.91 (-30.82, 32.63) for HR2 and -1.82 (-25.27, 21.63) for HR3. The ICC was 0.729 (p<.001) for HR1, 0.828 (p<.001) for HR2 and 0.958 (p<.001) for HR3. Bland-Altman plots and scatterplots showed good correlation without systematic error when comparing Apple Watch with ECG measurements. SDD for EE was 17.5 kcal. Bias and LoA were 30.47 (-3.80, 64.74). The ICC for EE was 0.797 (p<.001). The Bland-Altman plot and a scatterplot directly comparing Apple Watch and indirect calorimetry showed systematic bias with an overestimation of EE by the Apple Watch.
Conclusions:
In patients with cardiovascular disease the Apple Watch measures HR with clinically acceptable accuracy during exercise. If confirmed, it might be considered safe to incorporate the Apple Watch in HR-guided training programs in the setting of cardiac rehabilitation. However, the Apple Watch systematically overestimates EE in this group of patients. Some caution might therefore be warranted when using the Apple Watch for measuring EE.
Citation
Per the author's request the PDF is not available.
Copyright
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