February 28 — 29, 2008 Advisory Committee Meeting
Minutes
Subcommittee Report: Cardio-Respiratory Health
William Kraus, M.D., presented the subcommittee report on
cardio-respiratory health. Dr. Kraus opened with the thought that this area is
challenged by the fact that an exposure is a continuum; however, the outcomes in
this area are continuous. The subcommittee reviewed eight major findings.
There are favorable dose-response relationships between
increases of habitual physical activity and:
-
CHD morbidity and mortality
-
CVD morbidity and mortality
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Cerebrovascular disease and stroke
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Blood pressure control
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Atherogenic dyslipidemia
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Vascular health: brachial artery flow media dilation (BAFMD)
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Cardio-respiratory fitness
In analyzing the characteristics of the dose-response
relationships in observational and case-controlled studies increased intensity
bouts appears to be associated with more favorable outcomes; however, volume in
these studies are poorly controlled and it may be an important factor. In
experimental studies increased intensity does not always hold (i.e., HDL, TG).
Frequency and duration of activity in these studies are poorly studied.
Most, if not all CRH outcomes, are associated with favorable and
reproducible responses with weekly volume of 800 MET-minutes per week
(equivalent to 12 miles per week). This can be achieved and individualized with
combinations of intensities, durations and frequencies. In inactive individuals,
any goal should be built gradually.
The subcommittee reviewed the following 4 research questions and
summarized conclusions for each question:
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What is the relation between physical activity and the
prevention of cardiovascular disease morbidity and mortality?
Conclusions
Data from prospective cohort studies and case-control studies, between
1995-2007, support a strong and consistent inverse association between level
of physical activity and CHD or CVB morbidity and mortality. Men and women who report moderate levels of physical activity experience a 20%
- 25% lower risk that their least activity counterparts, while those reporting
high levels of activity experience a 30% - 35% lower risk than the least
active. This is based on 68 study groups in prospective cohort studies and
case-control studies with approximately 872,000 subjects.
The inverse relation is evident in men and women at all ages and based on very
limited data there does not appear to be any differences in the relationship
based on race or ethnicity.
The inverse relation between activity and CVD morbidity and mortality appears
to occur in normal weight, overweight and obese men and women.
-
What are the dose response relations between physical activity and
cardiovascular morbidity and mortality?
Conclusions
Much of the data since 1995 is on occupational work and commuting measuring
amount of activity performed per day or week with limited data on activity
intensity. The different measures make it difficult to draw conclusions across
all studies. Of 33 studies reporting analysis for significant dose-response, 21
were significant.
The data are consistent in showing significant benefit with 2 hours of
moderate-intensity activity or greater per week. Lower amounts of activity show
some benefit. Greater benefit is associated with higher levels of activity.
-
What is the relation between physical activity and the
prevention of cerebrovascular disease morbidity and mortality?
Conclusions
Based on 24 study groups in prospective cohort and case controlled studies there
is a reasonably strong and consistent inverse association for both men and women
between amount of habitual physical activity performed and morbidity and
mortality resulting from strokes.
Compared to the least active, persons reporting moderate or high levels of
physical activity have approximately a 25% lower risk of all and ischemic
stroke. The results shown are greater between study variability than data for
CHD and CVD.
-
What are the dose-response relations between physical activity
and cerebrovascular disease?
Conclusions
From 24 sex specific reports on physical activity and stroke, 12 reported an
analysis of dose-response.
Lower rates of stroke are consistently reported when 2 hours, or more, of
moderate-intensity activity per week is performed. Lower levels of activity are
inconsistently inversely related to strokes
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