Abstract 14958: Association of Smartwatch-Based Resting Heart Rate With Cardiorespiratory Fitness Measures From Cardiopulmonary Exercise Test in the Community

Introduction: Resting heart rate (HR) is an established predictor of cardiorespiratory fitness. Commercial smartwatches permit remote HR monitoring in real world settings over long periods of time, but the relations of smartwatch measured HR and cardiorespiratory fitness in the general public remain uncharacterized. Objective We aimed to examine the associations of resting HR measured with a smartwatch in the electronic Framingham Heart Study (eFHS) with multi-dimensional fitness assessment via cardiopulmonary exercise test (CPET). We hypothesized that participants with lower resting HR would have greater cardiorespiratory fitness. Methods: eFHS participants were enrolled at an FHS research exam (2016-2019) and provided with a study smartwatch that collected longitudinal HR data for up to 3 years. We identified participants’ HR measures in the sedentary state through a classification algorithm to calculate the average resting HR for each participant. At the same exam, participants underwent CPET performed on a cycle ergometer. Multivariable linear models were used to test the association of resting HR with CPET indices. We used P<0.05 for significance. Results: We included 1,051 participants (mean age 52±8 years, 59% women, mean resting HR 77±6 beats/min) with a median of 27,655 HR records for each individual, and median of 266 watch-wearing days. Higher individual resting HR was associated with a lower peak oxygen uptake (VO 2 ; both in ml/kg/min and % predicted), lower VO 2 at the ventilatory anaerobic threshold (VAT), higher (adverse) ventilatory efficiency (VE/VCO 2 ), and unfavorable blood pressure response to exercise (higher mean arterial pressure at 75 watts) ( Table ). Conclusions: Our findings suggest the feasibility of smartwatch-based HR assessment as an indicator of a broad array of cardiorespiratory fitness responses in the community, including measures of global fitness (peak VO 2 ), ventilatory efficiency, and blood pressure response to exercise.