Baroreceptor sensitivity is impaired in elderly subjects with metabolic syndrome and insulin resistance

Abstract

OBJECTIVE: Metabolic syndrome consists of a collection of cardiovascular risk factors and is considered to increase the risk of cardiovascular morbidity and mortality. This study aimed to investigate whether altered baroreflex sensitivity (BRS), a measure of cardiovascular autonomic control, is related to metabolic syndrome and insulin resistance. DESIGN AND METHODS: Spontaneously occurring fluctuations in blood pressure and heart rate were recorded during 5 min of controlled breathing in a population sample of 1016 subjects aged 70 (the Prospective Investigation of the Vasculature in Uppsala Seniors study). BRS was calculated through both sequence and frequency domain analysis in 77% of the sample. RESULTS: BRS was reduced in those with metabolic syndrome (n = 172, median 4.3 versus 5.7; P < 0.0001 after correction for heart rate, cardiovascular diagnosis and medication) and was reduced in proportion to the number of fulfilled National Cholesterol Education Program/Adult Treatment Panel III metabolic syndrome criteria (P < 0.0001). BRS was inversely related to insulin resistance, calculated by homeostatic model assessment (HOMA index; r = -0.18, P < 0.0001). CONCLUSIONS: Cardiovascular autonomic imbalance, measured as a reduced BRS, is present in metabolic syndrome and in subjects with insulin resistance. As BRS mainly reflects vagal activity, future prospective studies will address the possibility of vagal impairment in the pathogenesis of metabolic syndrome.