Longitudinal population-level changes in resting heart rate during the covid-19 pandemic: Impact of changes in sleep, circadian, and physical activity variables

Rezaei, N.; Grandner, M. A.

Introduction: Population-level objective estimates of changes in health metrics over the course of the COVID-19 pandemic are sparse. This study evaluated change in resting heart rate (RHR) determined by optical plethysmography and relationships to changes in other lifestyle health behaviors (sleep and activity). Methods: Data were obtained from N=197,988 Fitbit users who wore their heart-rate enabled Fitbit device to sleep and had detected sleep stages at least 10 days in the month of January, the baseline period;and synced their devices at least once in the last 10 days of April. In addition, potential participants needed to reside in one of 6 target cities: Chicago, Illinois;Houston, Texas;Los Angeles, California;San Francisco, California;New York City, New York;and Miami, Florida. Users who met these criteria were randomly selected. Daily RHR, sleep duration (minutes), sleep duration variability (standard deviation), bedtime, step count, and active minutes were estimated by the device. Differences between January (before the pandemic) and April (peak of stay-at-home orders) was computed. Correlations between change in RHR and change in other variables were evaluated, stratified by age and sex. Results: For all age groups, in both men and women, mean RHR declined from January to April by about 1bpm, with the highest reductions in the youngest adults (all p<1x10-100 ). In general, acrossboth genders and all age groups, reductions in RHR were correlated with greater sleep duration, delaying bedtime, reduced sleep variability, and more active minutes. Steps were also associated in younger (but not older) adults. Results for ages 18-29 and >=65 are displayed in the Table. Discussion: During the COVID-19 pandemic, RHR decreased robustly but very slightly. Reductionsin RHR were correlated with improvements in other health behaviors (sleep and activity). Causal relationships could not be evaluated, but future studies may explore whether even small changes in health behaviors can measurably impact population RHR.