AUTONOMIC ACTIVITY ASSESSED BY HEART-RATE SPECTRAL-ANALYSIS VARIES WITH FAT DISTRIBUTION IN OBESE WOMEN

Obesity in humans has been associated with altered autonomic nervous s ystem activity. The objective of this study was to examine the relatio nship between autonomic function and body fat distribution in 16 obese , postmenopausal women using power spectrum analysis of heart rate var iability. Using this technique, a low frequency peak (0.04-0.12 Hz) re flecting mixed sympathetic and parasympathetic activity, and a high fr equency peak (0.22-0.28 Hz) reflecting parasympathetic activity, were identified from 5-minute consecutive heart rate data (both supine and standing). Autonomic activity in upper body (UBO) vs. lower body obesi ty (LBO) (by waist-to-hip ratio) and subcutaneous vs. visceral obesity (by CT scan) was evaluated. Power spectrum data were log transformed to normalize the data. The results showed that standing, low-frequency power (reflecting sympathetic activity) and supine, high-frequency po wer (reflecting parasympathetic activity) were significantly greater i n UBO than in LBO, and in visceral compared to subcutaneous obesity. W omen with combined UBO and visceral obesity had significantly higher c ardiac sympathetic and parasympathetic activity than any other subgrou p. We conclude that cardiac autonomic function as assessed by heart ra te spectral analysis varies in women depending on their regional body fat distribution.