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Elevated heart rate variability in physically active postmenopausal women: a cardioprotective effect?
K P Davy1, N L Miniclier, J A Taylor
1Department of Kinesiology, University of Colorado, Boulder 80309, USA. Davy@ucsu.Colorado.edu
Insights
Physically active postmenopausal women have higher heart rate variability (HRV) and cardiac baroreflex sensitivity (SBRS) than less active women. This suggests a potential cardioprotective mechanism linked to physical activity.
Area of Science:
- Cardiovascular Physiology
- Exercise Science
- Women's Health
Background:
- Coronary heart disease (CHD) and cardiac sudden death (CSD) incidence increase post-menopause.
- Low heart rate variability (HRV) is a known risk factor for CHD and CSD.
- Physical activity is associated with lower CHD and CSD incidence in women.
Purpose of the Study:
- To test if HRV is greater in physically active postmenopausal women compared to less active controls.
- To hypothesize that greater HRV in active women is linked to elevated spontaneous cardiac baroreflex sensitivity (SBRS).
Main Methods:
- Measured HRV (time and frequency domains) and SBRS using the sequence method.
- Data collected during controlled breathing in supine, sitting, and standing postures.
- Included 9 physically active and 11 age-matched less active postmenopausal women.
Main Results:
- Physically active women had lower body weight, BMI, and body fat percentage, with higher maximal oxygen uptake.
- Active women exhibited significantly higher HRV across all postures and breathing conditions.
- SBRS was also significantly higher in active women, explaining ~70% of the variance in high-frequency HRV.
Conclusions:
- Physically active postmenopausal women demonstrate superior HRV compared to their less active counterparts.
- SBRS is a major determinant of HRV in active postmenopausal women, suggesting a role in cardiac autonomic regulation.
- Findings suggest a potential cardioprotective mechanism associated with physical activity in postmenopausal women.
Abstract:
Coronary heart disease (CHD) and cardiac sudden death (CSD) incidence accelerates after menopause, but the incidence is lower in physically active versus less active women. Low heart rate variability (HRV) is a risk factor for CHD and CSD. The purpose of the present investigation was to test the hypothesis that HRV at rest is greater in physically active compared with less active postmenopausal women. If true, we further hypothesized that the greater HRV in the physically active women would be closely associated with an elevated spontaneous cardiac baroreflex sensitivity (SBRS). HRV (both time and frequency domain measures) and SBRS (sequence method) were measured during 5-min periods of controlled frequency breathing (15 breaths/min) in the supine, sitting, and standing postures in 9 physically active postmenopausal women (age = 53 +/- 1 yr) and 11 age-matched controls (age = 56 +/- 2 yr). Body weight, body mass index, and body fat percentage were lower (P < 0.01) and maximal oxygen uptake was higher (P < 0.01) in the physically active group. The standard deviation of the R-R intervals (time domain measure) was higher in all postures in the active women (P < 0.05) as were the high-frequency, low-frequency, and total power of HRV. SBRS also was higher (P < 0.05) in the physically active women in all postures and accounted for approximately 70% of the variance in the high-frequency power of HRV (P < 0.05). The results of the present investigation indicate that physically active postmenopausal women demonstrate higher levels of HRV compared with age-matched, less active women. Furthermore, SBRS accounted for the majority of the variance in the high-frequency power of HRV, suggesting the possibility of a mechanistic link with cardiac vagal modulation of heart rate. Our findings may provide insight into a possible cardioprotective mechanism in physically active postmenopausal women.