Central adiposity and decreased heart rate variability in postmenopause: a cross-sectional study

Objective To investigate the impact of waist circumference (WC) on heart rate variability in 87 apparently healthy, postmenopausal women. Methods In this cross-sectional study, time-and frequency-domain heart rate variability indices were determined at rest and during sympathetic stimulation with mental stress. Patients were stratified according to WC >= or < 88 cm. The mean (+/- standard deviation) age was 55 +/- 5 years. The median time since menopause was 6 (range 1-22) years. Age and time since menopause were similar. Results The mean body mass index was 27.12 +/- 4.49 kg/m(2). Metabolic syndrome was diagnosed in 26 (29.5%) participants. Thirty-eight participants (43.6%) had hypertension. Women with WC >= 88 cm had higher body mass index, glucose and insulin (both fasting and after a 75-g oral glucose tolerance test), HOMA, triglycerides, and free androgen index (p < 0.05). The metabolic syndrome was more frequent in women with WC > 88 cm (24.13% vs. 5.74%; p < 0.01). At rest, women with WC > 88 cm presented lower vagal modulation, expressed by a reduction in the mean of all normal RR intervals (mean RR) (p < 0.01) and root mean square of successive differences of adjacent RR intervals (rMSSD) (p < 0.05) than women with WC < 88 cm. Mental stress significantly increased sympathetic modulation in both groups, expressed by reduction in high frequency (HF), increase in low frequency (LF) and LF/F ratio, and reduction in mean RR and rMSSD. Conclusions Less favorable metabolic profile and lower cardiac vagal modulation with preserved sympathetic responsiveness were found in participants with WC >= 88 cm, suggesting that central adiposity may be associated with decreased heart rate variability in apparently healthy, postmenopausal women.