Abstract
BackgroundLow bone mineral density (BMD) and subsequent fractures are a major public health problem in postmenopausal women. The purpose of this study was to use the aggregate data meta-analytic approach to examine the effects of ground (for example, walking) and/or joint reaction (for example, strength training) exercise on femoral neck (FN) and lumbar spine (LS) BMD in postmenopausal women.MethodsThe a priori inclusion criteria were: (1) randomized controlled trials, (2) exercise intervention ≥ 24 weeks, (3) comparative control group, (4) postmenopausal women, (5) participants not regularly active, i.e., less than 150 minutes of moderate intensity (3.0 to 5.9 metabolic equivalents) weight bearing endurance activity per week, less than 75 minutes of vigorous intensity (> 6.0 metabolic equivalents) weight bearing endurance activity per week, resistance training < 2 times per week, (6) published and unpublished studies in any language since January 1, 1989, (7) BMD data available at the FN and/or LS. Studies were located by searching six electronic databases, cross-referencing, hand searching and expert review. Dual selection of studies and data abstraction were performed. Hedge’s standardized effect size (g) was calculated for each FN and LS BMD result and pooled using random-effects models. Z-score alpha values, 95%confidence intervals (CI) and number-needed-to-treat (NNT) were calculated for pooled results. Heterogeneity was examined using Q and I2. Mixed-effects ANOVA and simple meta-regression were used to examine changes in FN and LS BMD according to selected categorical and continuous variables. Statistical significance was set at an alpha value ≤0.05 and a trend at >0.05 to ≤ 0.10.ResultsSmall, statistically significant exercise minus control group improvements were found for both FN (28 g’s, 1632 participants, g = 0.288, 95% CI = 0.102, 0.474, p = 0.002, Q = 90.5, p < 0.0001, I2 = 70.1%, NNT = 6) and LS (28 g’s, 1504 participants, g = 0.179, 95% CI = −0.003, 0.361, p = 0.05, Q = 77.7, p < 0.0001, I2 = 65.3%, NNT = 6) BMD. Clinically, it was estimated that the overall changes in FN and LS would reduce the 20-year relative risk of osteoporotic fracture at any site by approximately 11% and 10%, respectively. None of the mixed-effects ANOVA analyses were statistically significant. Statistically significant, or a trend for statistically significant, associations were observed for changes in FN and LS BMD and 20 different predictors.ConclusionsThe overall findings suggest that exercise may result in clinically relevant benefits to FN and LS BMD in postmenopausal women. Several of the observed associations appear worthy of further investigation in well-designed randomized controlled trials.
Highlights
Low bone mineral density (BMD) and subsequent fractures are a major public health problem in postmenopausal women
A modality-specific, joint reaction force meta-analysis that included studies published up to December 2004 found a statistically significant benefit of 0.006 g/cm2 in lumbar spine (LS) BMD and a non-significant benefit of 0.010 g/cm2 in femoral neck (FN) BMD as a result of high-intensity resistance exercise in postmenopausal women [49]. Another modalityspecific meta-analysis by the same research group which included studies published through December 2006 reported a non-statistically significant benefit in FN and LS BMD in postmenopausal women as a result of walking [50]. These findings suggest that walking, a lower impact, ground reaction force exercise, may have little benefit on FN and LS BMD in postmenopausal women
The purpose of this study was to use the aggregate data meta-analytic approach to determine the effects of ground and/or joint reaction force exercise on BMD at the FN and LS in postmenopausal women participating in exercise levels below that currently recommended for bone health [8]
Summary
Low bone mineral density (BMD) and subsequent fractures are a major public health problem in postmenopausal women. Osteoporosis is a major public health problem affecting an estimated 200 million women worldwide [1]. Congruent with osteoporosis is an increased risk for osteoporosisrelated fractures, especially in women during the postmenopausal years, generally considered to begin around 50 years of age [2]. The two most common sites for osteoporosis-related fractures are the hip and the spine, with an estimated worldwide prevalence of 1.1 million and 862,000, respectively, in women 50 years of age and older in the year 2000 [2]. In the United States, the total annual costs associated with osteoporosis-related fractures were more than $19 billion in 2005 with a predicted increase to $25.3 billion in 2025 [4]. The majority of the costs in 2005 were attributed to fractures of the hip (72%) followed by the spine (6%) [4]
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