Effects of Oestrogen Treatment on Skeletal Response to Exercise in the Hips and Spine in Postmenopausal Women: A Meta-Analysis

Background It is recognized that low oestrogen status impairs the skeletal response to mechanical loading in elderly women; therefore, oestrogen administration is expected to increase the osteogenic response to mechanical strain. Objectives This meta-analysis aimed to evaluate the combined effects of hormone replacement therapy (HRT) and exercise on femoral neck and lumbar spine bone mineral density (BMD) in postmenopausal women, in comparison with the effects of exercise-only intervention. Methods A systematic literature search was conducted in PubMed, Embase, SPORTDiscus and ProQuest up to May 1, 2014, to ascertain the influence of oestrogen administration and exercise on BMD in postmenopausal women. The study quality and potential publication bias of the included trials were evaluated. The primary end point was the change in BMD from baseline to follow-up. The effect sizes were estimated in terms of the standardized mean difference (SMD). Subgroup analysis was conducted on the basis of exercise categories. Results Six studies with a total of 764 postmenopausal women (aged between 51.8 +/- 2.9 and 68.0 +/- 3.0 years) met the inclusion criteria. The included studies had low and high levels of heterogeneity of hip outcomes (I-2 = 0.0 %) and spine outcomes (I-2 = 80.8 %), respectively. Fixed- and random-effects models were used for calculating the effect size estimates. The pooled effect sizes associated with the combined interventions of HRT and exercise were significant for femoral neck BMD (SMD 0.220, 95 % confidence interval [CI] 0.011-0.429, p = 0.039) and lumbar spine BMD (SMD 0.729, 95 % CI 0.186-1.273, p = 0.009) in comparison with the exercise-only intervention. The mixed loading exercise programmes were sensitive to HRT in preventing postmenopausal bone loss in the spine (SMD 1.073, 95 % CI 0.140-2.005, p = 0.024) in comparison with single-mode exercise. Conclusions Our findings indicate that oestrogen treatment significantly increases the skeletal response to exercise training in both the hips and the spine in postmenopausal women, which implies that the combination of oestrogen administration and exercise may generate greater effects.