Biomedical Engineering Reference
In-Depth Information
Robbins 2007
Michaelsson 2007
Kujala 2000
Hoidrup 2001
Prospective
Cohort Studies
Gregson 2010
Gregg 1998
Feskanich 2002
Benetou 2010
Kanis 1999
Case-control
Studies
Jaglal 1995
Women
Men
Farahmand 2000
Boonyaratavej 2001
0.0
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0.4
0.6
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1.0
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1.4
1.6
1.8
Relative Risk of Hip Fracture
Most Active versus Least Active
Fig. 1 Point estimates of relative risk (±95% confidence intervals) of hip fracture from studies
that examined multiple levels of physical activity (most active group versus least active group)
(i.e., can be asymptomatic) and because there is a lack of consensus on the degree
of vertebral deformity that constitutes a fracture. A number of observational
studies have evaluated whether physical activity is associated with reduced risk for
hip fracture [ 7 , 10 , 21 , 22 , 27 , 28 , 32 , 34 , 37 , 51 , 65 , 77 ]. In all of these studies, the
relative risk of hip fracture in the most active subgroup of the cohort was less than
in the least active subgroup, as evidenced by a relative risk ratio less than 1.0
(Fig. 1 ), but not all risk ratios were statistically significant. Based on these
observation studies, physical activity appears to reduce the risk for hip fracture in
both women and men.
It is difficult to determine the minimal physical activity exposure associated
with fracture protection from these studies because many used only categorical
levels of activity (e.g., low, medium, high). Among the studies that used quanti-
fiable metrics, the minimal levels of physical activity found to be significantly
associated with reduced fracture risk were: [9-14.9 MET-h/week (MET = met-
abolic equivalent, where 1 MET is an oxygen uptake of 3.5 mL/min/kg body
weight) of physical activity [ 22 ], [4 h/week of walking [ 22 ], [1290 kcal/week of
physical activity [ 27 ], and [1 h/week of physical activity [ 21 , 37 ]. These levels of
physical activity were associated with relative reductions in hip fracture risk of
33-41%. Although these observational studies provide a guideline for the volume
of physical activity likely to be effective, they do not indicate whether it was the
frequency, duration, or intensity of the activity that influenced fracture risk. Two
studies that categorized physical activity by intensity (e.g., easy vs. normal vs.
brisk walking pace) found that higher-intensity physical activity was associated
with reduced fracture risk [ 22 , 27 ]. Such observations are concordant with the
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