Obesity is a known risk for cardio-metabolic diseases such as hypertension, ischemic heart disease [1,2], type-2 diabetes mellitus [3] and comorbidities like obstructive sleep apnea [4]. Previous studies showed hemodynamic and autonomic alterations in lean compared to obese [5,6] such as increased resting heart rate (HR), blood pressure (BP) [5,7], muscle sympathetic nerve activity (MSNA) [5,7,8], left ventricular mass index [9] and low frequency spectrum of heart rate variability (HRV) [6]. Contrary to this, autonomic activity was also shown to decrease with obesity [10,11] and had inverse relationship with body fat percentage [1]. AbstractObjective: There could be progressive changes in hemodynamic and autonomic parameters causing cardiovascular damage from lean to morbid obesity. We aim to study resting and reactivity of hemodynamic and autonomic parameters to physical and mental stress in lean, overweight and obese subjects of the Oman Family Study (OFS). Materials and Methods:Normal subjects from OFS, grouped as lean (N=437; Males=194), overweight (N=366; Males=172) and obese (N=214; Males=90) based on WHO classification of BMI underwent impedance cardiography and spectral analysis to estimate hemodynamic and autonomic parameters at rest and during 3min of word conflict test (WCT) and cold pressor test (CPT). Results: At rest, overweight had high BP compared to lean, similar BP in overweight and obese and lowest stroke index (SI) in obese and low power spectral density (P<0.05) in obese compared to overweight. The changes (∆) in HR, mean BP, cardiac and peripheral resistance index were similar in 3 groups during WCT. Autonomic responses to WCT and CPT were similar in 3 groups. Obesity measures (BMI, % fat) showed monotonic correlations with resting hemodynamic and autonomic parameters and with ∆WCT and CPT HR and SI.

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