Elevated heart rate variability in physically active postmenopausal
women: a possible cardioprotective effect?.
Davy, Kevin P., Nadia L. Miniclier, J. Andrew Taylor, Edith T.
Stevenson, and Douglas R. Seals.
Departments of Kinesiology and Medicine (Cardiology), University of
Colorado, Boulder and Denver, CO1 and Hebrew Rehabilitation Center
for the Aged, Beth Israel Hospital and Harvard Medical School
Division on Aging, Boston, MA2
APStracts 3:0044H, 1996.
Coronary heart disease (CHD) and cardiac sudden death (CSD) incidence
accelerates after menopause, but is lower in physically active versus
less active women. Low heart rate variability 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
to less active postmenopausal women. If so, we further hypothesized
that the greater HRV in the physically active women would be closely
associated with an elevated spontaneous cardiac baroreflex
sensitivity (SBRS). Heart rate variability (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 yrs) and 11 age-matched controls
(age= 56+/-2 yrs). 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 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 to 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.
Received 29 June 1995; accepted in final form 5 January 1996.
APS Manuscript Number H597-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 January 96