8
of sporting and recreational activities. Regular stair climbing and strenuous sports
play were associated with reduced risk of CHD during 6–10 years of follow-up,
whilst student athleticism offered no protection. More recently, the Health
Professionals’ Follow-Up Study, that consisted of 44,452 health professionals fol-
lowed between 1986 and 1998, is noteworthy because of its large sample size and
rigorous methodology [ 29 ]. In this study, various forms of activity conferred protec-
tion against CHD, including regular walking (18% risk reduction) and 1 h of run-
ning per week (42% risk reduction). Men who increased their exercise intensity
from low to vigorous over time had a CHD risk reduction of 12%. There has been
considerable recent interest in the relationships between physical activity, sedentary
behavior and health. The culmination of this research was Ekelund and colleagues’
[ 30 ] in a review of 16 studies which included more than one million adults. They
found that sedentary behavior was associated with all-cause mortality in the entire
sample. Importantly, they also found that sedentary behavior was not associated
with all-cause mortality in those who were “highly active” (that is, those who
reported about 60–75 min per day of moderate activity) suggesting that high levels
of activity may offset the negative effects of sedentariness.
Although there is now irrefutable epidemiological evidence that regular physicalactivity plays an important role in the prevention of CVD, this evidence has been
largely derived from studies of white males. More recent studies have therefore
attempted to examine associations between physical activity and CVD risk in
women and non-white populations [ 31 , 32 ]. The major epidemiological studies on
physical activity and CVD among women have emerged from large American
cohorts such as the Nurse’s Health Study [ 33 ], Women’s Health [ 34 ], and Women’s
Health Initiative studies [ 32 ]. Across studies there appears to be a fairly consistent
inverse dose-response association between physical activity and CVD in women,
with minimal protection achieved at a level of at least 1 h per week of moderate
intensity exercise such as walking [ 35 ].
The association between vigorous-intensity activity and mortality may be stron-ger than the association between moderate-intensity activity and mortality, at least
in men [ 36 – 40 ]. Taken together, the epidemiological evidence supports the notion
that exercise should be at least moderate intensity and, for many men and women,
brisk walking offers protection from CVD [ 41 ]. Our understanding of the optimal
frequency, intensity, duration and type of activity for CVD risk reduction [ 42 , 43 ] is
still evolving. Several recent analyses of large scale population data have been use-
ful in trying to determine minimal and optimal physical activity dosage. For exam-
ple, 15 min a day or 90 min a week of moderate-intensity exercise was shown to
lower mortality risk in a sample of more than 400,000 adults from Taiwan [ 44 ]. Data
from a recent meta-analysis of nine cohort studies revealed that undertaking some
moderate to vigorous physical activity but less than the guidelines was associated
with 22% reduction in mortality risk [ 45 ]. In an analysis of over 600,000 adults
from the US and Europe, an upper threshold for longevity occurred at 3 to 5 times
the physical activity recommendation although the additional benefit over and
M. Hamer et al.