Abnormal Sympathetic Reactivity to the Cold Pressor Test in Overweight Humans

BACKGROUND Overweight individuals (body mass index (BMI) 25-29.9 kg/m(2)) are at higher risk for developing cardiovascular disease and hypertension when compared with lean individuals of normal weight (BMI 18.5-24.9 kg/m(2)). The purpose of this study was to test the hypothesis that exaggerated sympathetic nervous system responses to stressors may be one potential mechanism that predisposes overweight individuals to developing hypertension. METHODS We compared heart rate (HR), blood pressure (BP), and muscle sympathetic nerve activity (MSNA) using microneurography, in normotensive overweight individuals compared with age-matched lean controls, at baseline and during two sympathoexcitatory maneuvers: cold pressor test (CPT), and static handgrip exercise (SHG 30%). RESULTS During CPT, MSNA increased in both groups, but the magnitude of MSNA response was significantly greater (P = 0.03) in overweight (+18.1 +/- 2.8 bursts/min) compared with lean controls (+10.8 +/- 1.2 bursts/min). MSNA response to SHG at 30% maximum voluntary contraction (MVC) was similar between the two groups. There were no significant differences in systolic (SBP) or diastolic BP (DBP) responses or HR responses between the two groups during either maneuver. CONCLUSIONS Normotensive overweight individuals have an exaggerated MSNA response to the CPT. Augmented sympathetic reactivity to cold stress may contribute to increased risk of hypertension in overweight individuals.