February 28 - 29, 2008 Advisory Committee Meeting
Subcommittee Report: All-Cause Mortality
I-Min Lee, M.D., Sc.D. presented the subcommittee report on
all-cause mortality. The subcommittee reviewed 5 research questions:
Is there an association between physical activity and
mortality; what is the magnitude of the association?
What is the minimum amount of physical activity associated
with significantly lower mortality rates?
Is there a dose-response relation between physical activity
What is the shape of the dose-response between physical
activity and mortality?
Is the physical activity-mortality relation independent of
The subcommittee reviewed 83 potential studies from the CDC database and
ultimately included 73 studies in their research. All were observational studies
and almost all were prospective cohort studies. The studies were conducted in
North America, Europe, the Middle East, Asia and Australia. The samples
consisted of 254,514 men and 576,574 women of which there were 113,358 deaths.
60% of the subjects were 40 or older and 20% 65 or older. Most were Caucasian
and most were identified as healthy.
Dr. Lee summarized the subcommitteeâ€™s conclusions for question 1. There is
strong evidence of an inverse association between physical activity and
all-cause mortality. Active people have approximately a 30% lower mortality risk
compared with inactive people. The association is seen in men, women, young
people and old people in populations in both the U.S. and internationally among
different races as well as in people with high risk factors. One study of
disabled people also appeared to hold this relation.
For question 2, there is a challenge in quantifying the minimum amount of
physical activity associated with lower mortality rates are the different
assessments and categorizations of physical activity. Most studies measured
leisure-time physical activity but it would be helpful to also measure the
impact of routine physical activity. Ultimately, there is a challenge to
synthesize the data across all studies and express the findings in a fashion
that can be readily translated for public health purposes. The data is clear
however I showing that the equivalent of at least 2 to 2.5 hours per week of
moderate-intensity physical activity is associated with significantly lower risk
of mortality. It is important to note that this level does not represent an
Regarding question 3 on the dose-response relationship between physical activity
and mortality Dr. Lee summarized as follows. Most of the data in the studies
measured total volume of energy expended. The data consistently demonstrates an
inverse dose-response relationship. While the data shows that at least 2 to 2.5
hours of moderate-intensity activity per week is needed to significantly reduce
all-cause mortality rates, this amount does not represent a threshold level.
Rather, the dose-response relation supports a "some is good; more is better"
message. There is limited data showing that vigorous-intensity activity is
associated with additional risk reduction. There is no data on dose-response
relations for duration and frequency of physical activity, independent of their
contributions to total volume of energy expended.
Summarizing the conclusions for question 4 the dose-response curve appears
curvilinear. On average, across studies, compared to less than half an hour of
moderate-to-vigorous activity per week, 1.5 hours per week is associated with a
20% reduction in risk. Additional amounts of activity is associated with
additional risk reductions but at smaller magnitudes.
Finally, Dr. Lee, addressed the final research question looking into the
potential relation of adiposity to physical activity and mortality. The inverse
relation between physical activity and mortality appears independent of
adiposity. Additionally, a few studies have stratified findings by Body Mass
Index (BMI) and these studies show the inverse association between physical
activity and mortality is similar across strata of BMI.
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