The accuracy of blood pressure measurement by a smartwatch and a portable health device.

: Handheld medical devices and smartwatches that measure BP without a cuff have recently become available. Since these measurements are relatively more user-friendly than conventional cuff-based measurements they may aid in more frequent BP monitoring. We investigated the accuracy and precision of two popular cuff-less devices: the Everlast smartwatch and the BodiMetrics Performance Monitor. : We enrolled 127 patients from the Thomas Jefferson University Hospital Preadmission Testing Center. Research staff were trained to measure BP according to manufacturer guidelines for the investigational devices. The Everlast smartwatch provides measurements of systolic (SBP) and diastolic (DBP) BP, whereas the Bodimetrics only provides SBP. Reference BP measurements were obtained using a hospital-grade automated sphygmomanometer. After 5 minutes of quiet sitting, four standard and three investigational BP measurements were taken with sixty seconds in between each measurement. The reference BP value was calculated by determining the average of the 2 standard BP measurements that bounded the investigational measurements. We thus determined 3 comparison pairs for each investigational device in each subject. We calculated the mean (SD) of the absolute difference between the respective investigational devices and the reference for SBP and DBP. : Data from 42 individuals was excluded because of variation in standard BP measurements per prespecified rules. Of 85 participants used for analysis, 36 (42%) were women, the mean (SD) age was 53 (21) years, 32 (38%) self-reported hypertension, and 97% of these (n=31) reported taking antihypertensive medications. The average differences between the Everlast watch and reference were 16.9 (13.5) mm Hg for SBP and 8.3 (6.1) mm Hg for DBP. The average difference between the Bodimetrics performance monitor and the reference was 5.3 (4.7) mm Hg for SBP. : The Everlast smartwatch and the BodiMetrics Performance Monitor we tested are not accurate enough to be used as BP measurement devices.