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1 Department of Kinesiology and 2 Divisions of Cardiology and Geriatric Medicine, Department of Medicine, University of Colorado, Boulder, Colorado 80309
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
ACKNOWLEDGEMENTS
FOOTNOTES
REFERENCES
ABSTRACT 
Stevenson, Edith T., Kevin P. Davy, Pamela P. Jones,
Christopher A. Desouza, and Douglas R. Seals. Blood pressure risk factors in healthy postmenopausal women: physical activity and hormone
replacement. J. Appl. Physiol. 82(2):
652-660, 1997.
The prevalence of cardiovascular disease (CVD)
increases with advancing age in women, particularly after menopause.
CVD risk is lower in physically active women relative to their
sedentary peers, but the responsible mechanisms are not well
understood. The aims of this study were to test the hypotheses that
1) physically active postmenopausal
women demonstrate more favorable blood pressure (BP)-related risk
factors for CVD than do sedentary healthy women and
2) women on hormone replacement
therapy (HRT) also have more favorable levels of these CVD risk
factors. BP-related CVD risk factors were measured in physically active
women (n = 18; age 55 ± 1 yr;
n = 8 on HRT) and in healthy
less-active controls (n = 34; age 59 ± 1 yr; n = 17 on HRT). Maximal
oxygen consumption was higher in the active group, whereas waist-to-hip
ratio and waist circumference were lower (all
P < 0.005). The active
women demonstrated marginally lower (5-8 mmHg;
P 
0.10) levels of casual, 24-h, and
daytime systolic BP (SBP). They also tended to have lower
(P = 0.11) daytime SBP loads
(percentage of BP recordings >140/90 mmHg) and lower daytime and
nighttime BP variabilities (P = 0.04)
and a reduced (P < 0.007) SBP
response to submaximal exercise. Women on HRT tended to have lower
(3-4 mmHg; P = 0.07) levels of
24-h and nighttime diastolic BP (DBP) relative to the nonusers and
smaller (P < 0.04) daytime and 24-h
DBP loads. Stepwise multiple regression indicated that waist
circumference was the primary predictor of most of the SBP-related CVD
risk factors while HRT use was the best predictor for DBP loads. These
findings indicate that, in general, physically active postmenopausal
women demonstrate more favorable SBP-related CVD risk factors relative to their less-active healthy peers, which may be mediated, in part, by
their lower levels of abdominal adiposity. In addition, HRT use tends
to be associated with lower levels of DBP-related CVD risk factors.
body fat distribution; exercise; aging; hormone replacement therapy
INTRODUCTION CARDIOVASCULAR DISEASES (CVDs) are the leading cause of
death in middle-aged and older American women (3, 10, 15). The prevalence of CVD increases with age in women, rising sharply after
menopause (3, 10). Regular physical activity is associated with a
reduced risk of CVD in postmenopausal women (25). Our recent work (36)
and that of others (12, 13, 28) suggest that this protective effect may
be due at least in part to more favorable levels of various metabolic
risk factors, such as plasma lipids, fasting plasma glucose and insulin
levels, and glucose tolerance. It is also possible, however, that the
decrease in CVD risk in physically active women is associated with
reduced arterial blood pressure (BP)-related CVD risk factors. These BP behaviors include the following: elevated levels of casual BP at rest
(8, 34) and 24-h ambulatory BP (22, 24), elevated BP load (i.e.,
percentage of 24-h BP recordings exceeding 140/90 mmHg) (39), reduced
or absent nocturnal decline in BP (37), elevated BP variability (22),
and an augmented systolic BP (SBP) response to acute aerobic exercise
(5, 18).
Data on middle-aged and older US women indicate either lower or similar
levels of casual BP at rest in physically active compared with more
sedentary subjects (1, 26). However, there is very little information
on the relationship between physical activity levels and other
BP-related CVD risk factors. Accordingly, the primary purpose of the
present study was to test the hypothesis that highly physically active
postmenopausal women demonstrate more favorable BP-related risk factors
for CVD than do healthy nonobese but less-active controls.
Our subject population also allowed us to examine possible differences
in BP-related CVD risk factors in users vs. nonusers of hormone
replacement therapy (HRT), another factor that has been associated with
a reduced risk of CVD (3, 15). As with high physical activity levels,
however, it is not known whether HRT use confers its beneficial
effects, in part, through an association with reduced BP-related CVD
risk. Therefore, the secondary purpose of the present study was to
obtain preliminary information on this question.
To address these purposes, a cross-sectional model was used that we
have employed successfully in the past to gain insight into such issues
(30, 35). Specifically, BP-related CVD risk factors in middle-aged and
older highly physically active women were compared with those in
age-matched healthy nonobese sedentary controls.
METHODS Subjects
The physically active women were selected from participants in local and regional road-running races. The controls were recruited by advertisements in local newspapers. Those respondents who met the criteria of the study were invited to undergo a diagnostic treadmill electrocardiogram (ECG) test. If the test proved negative, they were accepted into the study. Approximately 40% of the active women contacted agreed to participate in the study, whereas only 10-20% of the respondents to the newspaper advertisements were eligible to serve as controls. Most of those responding were either too physically active or were currently taking medications that would influence the dependent variables of the study.
All subjects were free of overt coronary artery disease as assessed by medical history, physical examination, and resting and maximal exercise ECGs. Fifty-one of the 52 subjects were postmenopausal as documented by plasma follicle-stimulating hormone levels exceeding 30 mU/ml (32). One subject (a runner) was perimenopausal, but her data were included because they were not obviously different from the other subjects in her group and did not alter the mean values of the dependent variables. HRT was currently being used (for at least 1 yr) by 8 of the 18 (44%) physically active women and by 17 of the 34 (50%) controls. The majority (18 of 25) of the HRT users were receiving oral estrogen in combination with progesterone. Other regimens included oral estrogen alone (5), an estrogen patch (1), and a combined estrogen and progesterone patch (1). None of the subjects smoked or took other medications that could affect any of the dependent variables of the study.
The experimental protocol was approved by the Human Research Committee at the University of Colorado at Boulder; voluntary written informed consent was obtained from each subject after the nature, purpose, and risks of the study had been explained.
Measurements
Maximal oxygen consumption (
O2 max) was measured
by using on-line computer-assisted open-circuit spirometry during
incremental treadmill exercise, as described previously (35), and was
used as a measure of aerobic fitness. Physical activity level, defined as the estimated daily energy expenditure, was assessed by using the
Stanford Physical Activity Questionnaire (29). Body composition and
regional body fat distribution were estimated from various skinfold and
circumference measurements because of their potential influence on BP
behavior (38). All anthropometric measures were made by a single
investigator while the subject was in a standing position. Skinfolds
were measured at five body sites by using a Lange caliper. The sum of
these skinfolds was used to estimate percent total body fat (7). The
waist was measured at the narrowest part of the torso while the hip was
measured at the widest extension of the buttocks. The waist
circumference and waist-to-hip ratio were used as an index of an
abdominal or upper body fat distribution, respectively. To assess any
dietary influences on BP-related CVD risk factors, 3-day dietary
records were analyzed to provide an estimate of total caloric intake
and composition (Food Processor Plus, ESHA Research, Salem,
OR).
Casual BP at rest was measured by conventional sphygmomanometry by using guidelines established by the American Heart Association (23) while subjects were in the supine, sitting, and standing positions as described previously (31). Changes in SBP and diastolic BP (DBP) from the supine to standing position were used as a measure of autonomic nervous system and cardiovascular functions as well as BP tolerance to orthostatic stress.
BP recordings over a 24-h period of normal daily activity were made by using a noninvasive ambulatory monitor (model 90207, Spacelabs, Redlands, WA) as described in detail previously (31). The ambulatory system was calibrated against a mercury sphygmomanometer, and the cuff was programmed to inflate automatically every 15 min from 6 A.M. to 11 P.M. and every 20 min between 11 P.M. and 6 A.M.
Measuremens obtained from the ambulatory recordings included mean levels of 24-h, daytime, and nighttime SBP and DBP, where the nighttime period was individually defined as the period from when the subject went to bed at night until she arose the following morning and daytime was defined as the 24-h complement of night. Day-to-night differences in SBP and DBP were calculated to indicate the presence or absence of a nocturnal decline in BP. In addition, SBP load (percentage of SBP recordings exceeding 140 mmHg) and DBP load (the percentage of DBP recordings exceeding 90 mmHg) were determined from the ambulatory recordings. SBP and DBP variabilities were assessed as the SDs of the individual BP recordings over the 24-h period, during the day, and during the night (2, 27).
In accordance with established CVD risk factors associated with the BP
response to acute exercise (5, 18, 40), SBP was measured during
submaximal and maximal exercise, and the increases from preexercise to
submaximal and maximal exercise were calculated. To determine the SBP
response to submaximal exercise, BP was recorded during the 2nd min of
each 2-min stage of an incremental treadmill-walking protocol as
described previously (35). The SBP at the common workload of 6.4 metabolic equivalents (METs) (corresponding to a
O2 max of ~22
ml · kg
1 · min1)
was determined in each subject. This workload was selected because it
represented the highest submaximal level attained by all subjects in
the study. Maximal SBP was measured during the final minute of the
exercise protocol when the subject had attained maximal heart rate.
Both the absolute levels of SBP at submaximal and maximal exercise and
the magnitudes of the increases from standing rest were used to
characterize the submaximal and maximal SBP responses. In addition, the
percentage of subjects in each group whose SBP increased by >7
mmHg/MET from rest to submaximal exercise (~45 mmHg from rest to 6.4 METs) was calculated as an indication of an exaggerated SBP response
(19).
All measurements were made over a 2- to 3-wk period during three
separate sessions at least 72 h apart. Session
1 included the diagnostic treadmill ECG test, together
with instructions for completing the 3-day dietary records. During
session 2, the physical activity
questionnaire was administered, anthropometric measures were made, and
a treadmill
O2 max test
was performed. In the final session, casual BP was measured and the
subject was fitted with a 24-h ambulatory BP monitor.
BP has been reported to be reduced for up to 13 h after an acute bout of physical exercise (11). Therefore, to eliminate such effects while preserving as much as possible the normal biological state of the runners, all of the above BP measurements were obtained ~20 h after their last bout of exercise. In addition, the 24-h ambulatory BP recording for the active women was made on a nonexercise day.
Data Analysis
Differences in the dependent variables between the physically active women and the controls were assessed by multiple analysis of variance with subsequent post hoc analysis if the significance level was P < 0.05. Repeated-measures analysis of variance was used to determine differences when sequential measures were made. Univariate correlational analysis was used to assess relationships between physical activity levels,O2 max, body
composition, diet, HRT use, and the other dependent variables of the
study. Forward stepwise multiple regressions were used to assess the relative contributions of the above factors to the BP-related risk
factors of the study.
RESULTS
BP-Related CVD Risk Factors in Physically Active vs. Less-Active Women
Physical characteristics (Table 1). The physically active women and controls were similar in age, height, and estimated fat-free mass, whereas body weight, waist-to-hip ratio, body mass index (BMI), sum of skinfolds, estimated percent body fat, and waist circumference were lower (P < 0.01) in the active women. In addition,O2 max and
levels of physical activity were higher
(P < 0.01) in the active women vs.
the controls.
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O2 max levels were
daytime SBP and DBP variability (r = 
0.33 to 0.36; P < 0.02), as well as both the absolute level of SBP at the submaximal workload of 6.4 METs (r = 0.30
to 0.33; P < 0.05) and the
increase in SBP from preexercise levels to this submaximal exercise
workload (r = 0.41 to
0.55; P < 0.005). In
addition, there were inverse relationships between physical activity
and daytime DBP variability as well as between
O2 max and 24-h,
daytime, and casual SBP, 24-h and daytime SBP variability, nighttime
DBP variability, and daytime SBP load
(r = 0.28 to 0.34; all
P < 0.05). When stepwise multiple
regression was performed,
O2 max was a
significant predictor of 24-h SBP variability and levels of SBP before
treadmill exercise and at maximal exercise.
Relationships among regional body fat distribution, diet, and
BP-related CVD risk factors.
Univariate analysis indicated that the major correlates of casual
resting and ambulatory (24-h, daytime, and nighttime) SBP, as well as
SBP load, were waist circumference (r = 0.38-0.55; P < 0.02), BMI
(r = 0.29-0.42;
P < 0.04), and sum of skinfolds (r = 0.28-0.38;
P < 0.05). When forward stepwise
multiple regression was performed, waist circumference appeared as the
primary predictor of all of the above SBP measures, accounting for
15-31% of the observed variance. In addition, whereas univariate
analysis indicated that waist circumference, BMI, and sum of skinfolds
were all related to nighttime BP variability
(r = 0.28-0.51;
P < 0.05), waist circumference was
the only significant predictor (forward stepwise multiple regression),
accounting for 21 and 31% of the variance in DBP and SBP
variabilities, respectively. Absolute levels of SBP immediately before
and during submaximal (6.4 METs) and maximal exercise, as well as the
increase in SBP from rest to submaximal exercise, were all related to
waist circumference (r = 0.29-0.65; P < 0.05), which was
also the primary predictor of each of these exercise BP measurements
(accounting for 10-45% of the variance).
Dietary measures, including macronutrient and total caloric intakes,
were not related to any of the BP-related CVD risk factors by either
univariate analysis or forward stepwise multiple regression.
BP-Related CVD Risk Factors in HRT Users vs. Nonusers
Physical characteristics. There were no differences in the physical characteristics, including body composition,O2 max, and levels of
physical activity, of the users (n = 25) and nonusers (n = 27) of HRT. In
addition, the dietary intake and composition of these two groups were
similar.
Casual and ambulatory BP recordings (Table
6).
Levels of casual SBP and DBP at rest were not significantly different
in the two groups. The ambulatory recordings showed a trend for lower
(3-4 mmHg; P = 0.07) 24-h and
nighttime DBP in the HRT users. Both daytime and 24-hr DBP loads (Fig.
1) were substantially lower in the HRT
users vs. nonusers (2 ± 5 vs. 10 ± 14% for 24-h; 5 ± 10 vs. 13 ± 19% for daytime;
P < 0.04 for both). However, there
were no group differences in SBP loads or BP variability.
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) vs. nonusers (
) of hormone replacement therapy.
Values are means ± SE. BP load is defined as percentage of BP
recordings over a 24-h period that exceed 140/90 mmHg.
* P < 0.02.
SBP responses to submaximal and maximal exercise. There were no differences in the absolute levels of SBP during preexercise standing rest, submaximal exercise at 6.4 METs, and maximal exercise in the HRT users vs. nonusers. There were also no differences in the increases in SBP from rest in response to both submaximal and maximal exercise in the two groups.
DISCUSSION
To our knowledge, this study is the first to address the question of whether BP-related CVD risk factors, considered collectively, are more favorable in physically active aerobically fit postmenopausal women compared with their sedentary peers. Such a finding could explain, at least in part, the lower prevalence of CVD in the former (25). Our results suggest that, in general, highly physically active postmenopausal women demonstrate more favorable SBP-related CVD risk factors relative to healthy nonobese but less-active women of the same age, which may be mediated, at least in part, by a lower level of abdominal fat, as estimated by waist circumference.
A secondary aim of this study was to determine whether BP-related CVD risk factors are lower in healthy postmenopausal women on vs. not on HRT. In contrast to physical activity levels, HRT was primarily associated with DBP. Specifically, DBP loads were lower, and there was a strong tendency for lower levels of 24-h and nighttime DBP in the HRT users.
Casual BP at Rest
Elevated levels of casually determined BP at rest have consistently been associated with a higher incidence of coronary arterial disease and a greater risk of future cardiovascular morbidity (9). Epidemiological studies report both lower and similar levels of casual resting BP in physically active vs. sedentary adults; however, most of these studies were on men (1).An earlier cross-sectional study by Reaven et al. (26) showed a strong inverse relationship between physical activity and SBP levels in women. They reported unadjusted levels of resting SBP of 143 mmHg in the sedentary women vs. 123 mmHg in the most-active women. Consistent with our results, however, there was no effect of physical activity status on DBP at rest. The greater SBP differences observed in physically active vs. sedentary women in the two studies are likely explained by the fact that the sedentary controls in the Reaven et al. study were older, on average, than ours and included women with established hypertension or evidence of coronary heart disease (CHD). Thus the results of the present study extend these earlier findings by demonstrating that the effects of habitual physical activity per se (i.e., independent of disease, and so on) on SBP at rest are relatively modest in healthy middle-aged and older women. Moreover, our findings and those of Reaven and colleagues document that physical activity levels have no obvious influence on DBP in normotensive postmenopausal women.
In addition to physical activity, there is some evidence that aerobic
fitness, as assessed by time to exhaustion during graded treadmill
exercise, is associated with reduced levels of casual BP in women (6).
The significant correlation between casual levels of SBP and
O2 max observed in the
present study supports this earlier observation.
There is little information concerning the relationship between HRT and casual BP levels at rest. An earlier study (17) reported no significant differences in casual BP in users vs. nonusers of HRT, which is consistent with the findings of the present study.
In the present study, waist circumference was the strongest correlate and predictor of casual SBP. Its predictive importance may explain, in part, the 5- to 8-mmHg differences we observed in levels of casual SBP between the physically active women and controls because the physically active women had lower waist circumferences. It may also explain the lack of differences in casual SBP in the users vs. nonusers of HRT because waist circumferences were similar in these two groups. Previous studies also support a relationship between central body fat distribution and elevated casual SBP at rest in both men and women over a wide age range (4).
Twenty-Four-Hour Ambulatory BP
Because of the high variability in casual BP readings, 24-h recordings provide a more reliable indicator of overall BP levels during typical daily activities (41). Twenty-four-hour ambulatory recordings have been shown to be more strongly correlated with target organ damage than is casual BP (24). In the present study, daytime ambulatory SBP in both the physically active women and the controls was 11-12 mmHg higher than casual SBP, calculated as the mean of the BP levels in the supine, standing, and sitting positions (Table 2). This finding is consistent with that reported by Zachariah et al. (41) in their recent study on ambulatory SBP characteristics in healthy normotensive men and women 20-84 yr of age.In the present study, 24-h, daytime, and nighttime SBP levels were consistently ~5 mmHg lower in the active women, whereas DBP levels were similar. This is consistent with results from a recent study on physically active vs. nonphysically active men (21). To our knowledge, there are no other cross-sectional data relating physical activity or aerobic fitness to 24-h BP in women.
In the present study, waist circumference and, to a lesser extent, BMI and sum of skinfolds were significantly related to 24-h, daytime, and nighttime SBP (by univariate analysis), but waist circumference was the only significant independent predictor. There were no significant correlates or predictors of 24-h, daytime, and nighttime DBP. These findings may explain the differences we observed in ambulatory SBP between the physically active and sedentary women (waist circumferences were lower in the physically active women). We are unaware of previous data relating regional fat distribution to 24-h ambulatory BP levels.
BP Load
Results of a study by White et al. (39) indicate that measurement of BP load is a better predictor of target organ damage (e.g., left ventricular hypertrophy) than are both casual and 24-h ambulatory BP measurements (41). The absolute levels of BP load observed in our study were generally consistent with those reported in a recent study for normotensive postmenopausal women (41).We are aware of no previous cross-sectional findings on BP loads in women (or men) differing in levels of physical activity, aerobic fitness, or use of HRT. We found that active fit postmenopausal women had lower SBP loads than did sedentary women. Because ~24% of the variance in 24-h and daytime SBP loads was accounted for by waist circumference, the lower waist circumferences in the active women may explain their reduced SBP loads.
Markedly lower DBP loads were observed in the users vs. nonusers of HRT. Specifically, the majority (>50%) of the HRT users had all of their DBP readings below 90 mmHg, whereas only 21% of the nonusers satisfied this condition. Thus our findings suggest that a lower 24-h DBP load could contribute to the lower risk of CVD in postmenopausal women on HRT.
Nocturnal BP Decline
Blunted or absent nocturnal fall in BP has been associated with increased target organ damage in women, but not men, with essential hypertension (37). Verdecchia et al. (37) reported an 11% nocturnal decline in SBP and a 16% decline in DBP in a group of 25 postmenopausal women who were free of CHD. In the present study, physical activity status was not associated with nocturnal decline in BP. Our values (12% for SBP and 16-17% for DBP) were similar to those reported by Verdecchia and colleagues. The relative nocturnal SBP and DBP declines for the users and nonusers of HRT were not significantly different. Overall, no significant univariate correlates or predictors (using stepwise multiple regression) of nocturnal BP decline were found. To our knowledge, the present study is the first to investigate these relationships.BP Variability
High BP variability as assessed by intra-arterial BP recordings has been associated with an elevated prevalence and severity of target organ damage (22), as well as with vascular structural changes (27). BP variability, as measured by the SD of ambulatory recordings, has been shown to be similar to that obtained from continuous intra-arterial monitoring, provided that the interval between two subsequent measurements does not exceed 20 min (2), a condition satisfied in the present study. Furthermore, our values for BP variability compare favorably with those in a previous study by Mancia et al. (14), which were calculated from intra-arterial BP recordings over a 24-h period.The present study demonstrated significantly lower daytime and nighttime BP variability in the physically active women vs. controls. This may be due, in part, to the finding that waist circumference, which was lower in the physically active women, was the primary determinant of SBP and DBP variabilities in the pooled population. This finding may also explain why BP variability did not differ between the users and nonusers of HRT: waist circumference did not differ between these two groups. We are aware of no previous cross-sectional studies that have reported body composition or HRT correlates of BP variability.
SBP Response to Acute Exercise
The SBP response to acute exercise has been expressed in the literature in several ways, including 1) the absolute level of SBP at a given submaximal workload (18), 2) the absolute level of SBP at maximal exercise (40), and 3) the increase in SBP from rest to a predetermined level of submaximal exercise (5). An augmented SBP response to both acute submaximal and maximal exercise is associated with both future hypertension in normotensive individuals (1) and cardiovascular mortality in mildly hypertensive middle-aged men (18).Previous studies on physically active vs. sedentary healthy postmenopausal women have reported both lower (20) and similar (16) absolute levels of SBP in response to submaximal and maximal exercise in the active women. The finding in the present study of a lower absolute level of SBP as well as a smaller increase in SBP above preexercise levels among the physically active women in response to the same submaximal workload is likely due to their superior level of aerobic fitness: the same absolute workload represents a lower relative workload to the active women. This finding is also consistent with the smaller waist circumferences, the primary predictor of these exercise BP responses, found in the active women. These findings, together with those from the two previous studies described above (16, 20), are consistent with a lower SBP response to exercise in physically active postmenopausal women.
Very little data are available concerning the SBP response to acute exercise in users vs. nonusers of HRT. A previous study by Martin et al. (16) reported lower levels of DBP and a trend for lower levels of SBP at rest and during submaximal and maximal exercise in small groups of older women who were using HRT relative to nonusers. In the present study, there were no significant differences in the SBP responses to submaximal and maximal exercise in HRT users vs. nonusers. Therefore, the available data do not support a strong association between HRT use and the SBP response to acute exercise.
Clinical Significance
Considered together, the present results indicate that highly physically active postmenopausal women demonstrate lower SBP-related CVD risk factors than do healthy but less-active women of similar age. These differences in SBP-related CVD risk factors may be partially mediated by lower abdominal adiposity as indicated by the lower waist-to-hip ratios and waist circumferences of the active women. This finding of lower SBP-related CVD risk factors in physically active middle-aged and older women may contribute to their lower prevalence of CVD.It is important to note that, although the lower levels of casual SBP (5-8 mmHg) and DBP (2-3 mmHg) in the physically active vs. sedentary women did not achieve statistical significance, they may be of clinical relevance. Although both groups had casual SBP levels in the normotensive range (mean of 113 mmHg for the active women; 118 mmHg for the sedentary women), the slightly higher levels in the sedentary women placed them at a significantly elevated risk of CHD mortality based on current epidemiological data (33). Furthermore, it has been estimated that in a normotensive population, a 5-mmHg lower SBP is associated with a 7-14% lower mortality (34) while a 1- to 3-mmHg lower DBP could reduce the incidence of future hypertension by 20-50% (33). Hence, the tendency for lower mean levels of SBP and DBP observed in the physically active postmenopausal women of the present study could have important implications for their future cardiovascular health.
Limitations
There are four limitations in the present study that we wish to emphasize. First, with the cross-sectional design employed it is possible that genetic or other constitutional factors may have influenced BP-related CVD risk factors independent of physical activity or other factors associated with our group comparisons. Hence, it is not possible to determine whether physical activity led to the observed favorable SBP-related CVD risk factors in the active women or whether their lower SBP risk profile is part of a broader phenotype that includes a high level of physical activity and fitness.Second, our subjects were healthy with mean levels of casual BP in the normotensive range. If a less-healthy control group had been used for comparison to the physically active women, it is likely that greater differences in BP-related CVD risk factors would have been observed in the active vs. sedentary women.
Third, although the age range of the women in our study extended to 70 yr, the mean ages of the two groups were 55-59 yr. It is possible that habitual physical activity has a greater impact on BP-related risk factors in a more uniformly older group of postmenopausal women than that studied here.
Finally, the measurement of BP at least 20 h after the last bout of exercise in the physically active women eliminated any potential effects of postexercise hypotension (11). Hence, because these women exercise most days of the week, we likely overestimated the daily BP levels of these active women. If so, the contribution of their lower BP-related risk to the lower prevalence of CVD observed in this population may be underestimated.
Conclusions
In general, highly physically active postmenopausal women demonstrate lower levels of SBP-related CVD risk factors relative to healthy nonobese but less-active women. This effect, which appears to be mediated in part by lower levels of abdominal adiposity, may play a role in the lower prevalence of CVD observed in physically active middle-aged and older women.In addition, users of HRT demonstrated lower DBP loads, as well as a strong tendency for lower levels of 24-h and nighttime DBP. This, too, could contribute, in part, to the link between HRT use and reduced risk of CVD.
ACKNOWLEDGEMENTS
This study was supported by Andrus Foundation Grant AARPAF-OCG0937B and National Institutes of Health (NIH) Grants HL-39966, AG-06537, and AG-13038. E. T. Stevenson, K. P. Davy, and P. P. Jones were supported by NIH Individual National Research Service Awards HL-08870, HL-08834, and AG-05705, respectively. D. R. Seals was supported in part by NIH Research Career Development Award AG-00423.
FOOTNOTES
Address for reprint requests: E. T. Stevenson, Univ. of Colorado, Dept. of Kinesiology, Campus Box 354, Boulder, CO 80309.
Received 28 June 1995; accepted in final form 23 September 1996.
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