Severe obesity is independently associated with elevated 24-hour ambulatory heart rate in hypertensive outpatients

Background and aims: Elevated heart rate (HR) is an established cardiovascular risk marker, yet its ambulatory profile across body mass index (BMI) strata in hypertensive patients remains incompletely characterized. We investigated the association between BMI and office and ambulatory HR, and explored heart rate variability (HRV), in a large real-world cohort of hypertensive outpatients. Methods and results: In this retrospective observational study 10,003 consecutive adult outpatients undergoing standardized office and ambulatory blood pressure monitoring (ABPM) were stratified by BMI (<25, 25-29, 30-34, and ≥35 kg/m2). Mean HR was assessed at office and during 24-h, daytime, and night-time periods. HRV was estimated as the coefficient of variation (CV%) of ambulatory HR. Multivariable models were adjusted for age, sex, systolic blood pressure, and negative chronotropic therapies. Increasing BMI was associated with a graded rise in HR across all settings (P < 0.001). Compared with normal-weight individuals, patients with BMI ≥35 kg/m2 showed higher office HR (79.6 vs 75.7), higher 24-h HR (76.7 vs 72.5), and higher night-time HR (70.8 vs 65.3 bpm) (all P < 0.001). These associations remained significant after multivariable adjustment and were consistent in both treated and untreated patients. Restricted cubic spline analyses suggested a non-linear relationship between BMI and ambulatory HR. HRV was lower in severe obesity, particularly during the 24-h and night-time periods, although associations were modest in continuous analyses. Conclusions: In hypertensive outpatients, severe obesity is independently associated with higher office and ambulatory HR across the 24-h period, defining a distinct chronotropic phenotype. Alterations in ambulatory HRV appear less pronounced.