Cardiovascular
Associations between heart rate variability from wearable devices and cardiovascular risk factors Yi-Hsuan Wu* Yi-Hsuan Wu Wu Wu Wu Wu Wu Wu Wu Wu Wu Stanford Prevention Research Center, Department of Medicine, Stanford School of Medicine, Stanford University, Stanford, CA, USA; Department of Epidemiology and Population Health, Stanford School of Medicine, Stanford University, Stanford, CA, USA
Heart rate variability (HRV) is a noninvasive marker of autonomic nervous system (ANS) function and cardiovascular disease (CVD) risk but is typically assessed using electrocardiography in clinical settings. Wearable devices enable continuous monitoring of HRV outside clinics and may support early detection of changes in cardiovascular function. This longitudinal study examined whether wearable-derived HRV is associated with established CVD risk factors. We analyzed data from 69 U.S. participants (aged 24-77 years; 78.3% female) in the Stanford WELL Wearable Pilot Study who wore photoplethysmography (PPG)-based smartwatches continuously for up to 60 days between July 26 and September 23, 2021. Pulse-to-pulse intervals were derived from PPG signals collected under free-living conditions, and frequency-domain HRV metrics were calculated. Analyses focused on the LF/HF ratio during sleep for the first seven weeks of monitoring, when motion effects were minimized and data completeness was highest. The LF/HF ratio was used as an indicator of autonomic modulation in this context. Hypertension, hyperlipidemia, sleep quality (Pittsburgh Sleep Quality Index), and covariates were assessed by baseline survey. Participants were classified into low, medium, and high sleep LF/HF ratio groups based on the median of weekly mean values. Compared with the low LF/HF group, higher LF/HF groups were less likely to have hypertension, hyperlipidemia, and poor sleep quality, although differences were not statistically significant. After adjustment for age, sex, body mass index, physical activity, and history of clinical depression, the medium (OR = 0.07; 95% CI: 0.01-0.58) and high LF/HF groups (OR = 0.01; 95% CI: 0.00-0.15) had lower odds of hypertension. These findings suggest that higher sleep HRV-derived LF/HF ratios, reflecting more preserved ANS regulation during sleep, are relevant to blood pressure-related CVD risk.