Author Affiliations: Department of Epidemiology and Biostatistics and Department of Medicine, University of California, San Francisco.
Estrogen has been used for many years to prevent bone loss and fractures
in postmenopausal women. Support for this practice comes from 2 lines of evidence.
First, observational studies consistently suggest that postmenopausal hormone
therapy reduces the risk of hip and other types of fracture.1,2
However, observational studies are susceptible to selection bias and confounding.
This may be especially true of studies of hormone therapy because users tend
to be healthier, wealthier, and more active than nonusers.3
Even if observational studies are qualitatively correct, they may overestimate
the degree of risk reduction attributed to hormone therapy.
Grady D, Cummings SR. Postmenopausal Hormone Therapy for Prevention of FracturesHow Good Is the Evidence?. JAMA. 2001;285(22):2909-2910. doi:10.1001/jama.285.22.2909