The impact of the components of metabolic syndrome on heart rate variability: Using the NCEP-ATP III and IDF definitions

Background: This study examined the relationship between metabolic syndrome (MetS) and heart rate variability (HRV) in Korean adults. Methods: Data were collected from family health examinations performed from December 2003 through January 2004, and 1,041 subjects consisting of males and females aged 20-87 years were included in this study. Measurement of the 5-minute HRV and several examinations for MetS were completed. The HRV was analyzed in both the time domain with the standard deviation of NN (SDNN) intervals and the frequency domain with the low frequency (LF) and high frequency (HF) components. MetS was defined by the criteria of the National Cholesterol Education Program's Adult Treatment Panel III (NCEP-ATP III) and the International Diabetes Federation (IDF). Results: There were significant differences in the MetS components and HRV indices between the two groups (with vs without MetS). The adjusted means of the HRV indices in the group with MetS were significantly lower than those in the group without MetS (P < 0.05). Furthermore, a significant negative correlation was found between all components of MetS and the HRV indices; additionally, as the number of MetS components increased, the HRV indices gradually decreased. Conclusions: Decreased cardiac autonomic tone was strongly associated with an increased cardiovascular risk, and HRV measurement could become an indispensable part of evaluating one's risk of cardiovascular disease, though we currently do not have sufficient information to identify the cutoff values for the HRV indices.