Hormone therapy and skeletal muscle strength: a meta-analysis

Abstract

Background: Our objective was to perform a systematic review and meta-analysis of the research literature that compared muscle strength in postmenopausal women who were and were not on estrogen-based hormone therapy (HT).

Methods: Twenty-three relevant studies were found. Effect sizes (ESs) were calculated as the standardized mean difference, and meta-analyses were completed using a random effects model.

Results: HT was found to result in a small beneficial effect on muscle strength in postmenopausal women (overall ES = 0.23; p = .003) that equated to an approximately 5% greater strength for women on HT. Among the 23 studies, various muscle groups were assessed for strength, and those that benefitted the most were the thumb adductors (ES = 1.14; p < .001). Ten studies that compared muscle strength in rodents that were and were not estradiol deficient were also analyzed. The ES for absolute strength was moderate but not statistically significant (ES = 0.44; p = .12), whereas estradiol had a large effect on strength normalized to muscle size (ES = 0.66; p = .03).

Conclusion: Overall, estrogen-based treatments were found to beneficially affect strength.

Figure 1.

Forest plot of effect sizes (ESs) from the 23 studies that assessed muscle strength in postmenopausal women who were and were not on hormone therapy (HT). A square represents the ES for a given study with the size of the square being proportional to the weighting of that study in the meta-analysis. A horizontal line indicates the ES’s 95% confidence interval (CI). Studies are arranged from lowest to highest ESs. The diamond at the bottom represents the overall ES for HT on muscle strength. The width of the diamond represents the 95% CI for the overall ES. *Combined study data for Sipila et al. (2001) and Taaffe et al. (2005).

Figure 2.

Forest plot of effect sizes from the meta-analysis conducted on the five studies that reported muscle strength normalized to muscle size in postmenopausal women who were and were not on hormone therapy (HT). *Combined study data for Sipila et al. (2001) and Taaffe et al. (2005).

Figure 3.

Forest plot depicting analysis of the moderator variable, muscle group type. Effect sizes (ESs) were compared between studies that measured strength of five different muscle groups. A diamond represents the combined ES for that level of the moderator variable. *Combined study data for Sipila et al. (2001) and Taaffe et al. (2005).

Figure 4.

Forest plot depicting analysis of the moderator variable, species type, in the meta-analysis of estradiol’s effect on absolute strength in rodents. E₂ deficient represents rodents that were ovariectomized. E₂ replete represents control rodents (e.g., sham-operated rodents) or rodents that were ovariectomized and treated with estradiol.

Figure 5.

Forest plot of effect sizes from the meta-analysis conducted on the seven studies that reported muscle strength normalized to muscle size in rodents that were estradiol deficient and estradiol replete.