The effect of obesity combined with low muscle mass on cardiac autonomic nervous system in healthy workers

Abstract

Objects: This study aims to examine the relationship between obesity combined with low muscle mass and cardiac autonomic nervous system by using heart rate variability (HRV) as measure of the parasympathetic and sympathetic modulation in healthy workers.Methods: The total subjects consisted of 1150 workers with a mean age of 43.55±11.45. The demographic information was asked to self-questionnaire and body composition was measured by bioelectrical impedance analysis. The muscle mass was calculated as the ratio of appendicular skeletal muscle mass and height squared. The subjects were classified as low muscle mass if their appendicular skeletal muscle mass was below the 50th percentile of the study sample and were classified as obesity if their body mass index (BMI) was above the 25kg/m2. Electrocardiography recording were obtained for 5 minutes and the time-domain and frequency-domain indices of HRV were analyzed.Results: The significant decrease of low frequency (LF) power and the standard deviation of normal to normal intervals (SDNN), which reflects sympathetic interactions and baroreceptor activity, are indicative of lower sympathetic in obesity and high muscle mass (OHMM) group and obesity and low muscle mass (OLMM) group than high muscle mass and non-obesity (HMM) group.The significant decrease of high frequency (HF) power and square root of the mean squared differences of successive differences (RMSSD), which reflects efferent parasympathetic activity, are indicative of reduced parasympathetic modulation in OHMM and OLMM groups. Also, OLMM group had lower HF power than OHMM.There is no significant difference in LF:HF ratio, which are indicative vagal modulation and sympathovagal balance.Conclusions: The OHMM and OLMM groups had lower HRV indices than HMM group. When comparing between OHMM and OLMM group, OLMM group had lower parasympathetic modulation than OHMM.