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August 15, 2002

Group Health study shows strong link between Depo-Provera and bone loss; but the loss is largely reversible

Seattle—Depo-Provera, an injectable form of birth control particularly popular among young and low-income American women, is strongly associated with bone loss, according to a recent study conducted at Group Health Center for Health Studies. The research, published in the September 2002 issue of Epidemiology, also found that the bone loss appears to be largely reversible once the injections are discontinued.

Loss of bone density increases the risk for osteoporosis, a disease in which bones become fragile and are more likely to break. Group Health scientists, in one of the most thorough studies of the issue to date, found that women who used Depo-Provera continuously for three years experienced about the same amount of bone loss as women who are breast-feeding or going through menopause.

"Bone loss is certainly a concern, but the study is also reassuring since it showed that women steadily regained bone density once they stopped using the contraceptive," said Delia Scholes, PhD, associate investigator at the Center and the principal investigator for this study.

Some earlier studies have found an association between Depo-Provera use and decreased bone density, while others have not. However, many of the previous studies only measured subjects’ bone density and their exposure to Depo-Provera at a single point in time, rather than following women forward over time. Because both new and long-term users were enrolled in the study, researchers could assess both short-term and long-term changes. Furthermore, only one previous study looked at the effects on bone density of stopping Depo-Provera use.

About 2 percent of American women who use contraceptives use Depo-Provera. However, rates are higher for younger women. Among women 15–19 years of age, 8 percent of non-Hispanic white women and 19 percent of non-Hispanic black women who use birth control use Depo-Provera.

Depo-Provera, which is given once every three months via injection, is relatively low-cost, private, and easy-to-use, said Scholes. It is a popular choice among women for whom other types of contraception have not worked well, she added.

"Choosing a contraceptive involves a highly individualized set of decisions," Scholes said, adding that she hopes the findings will alert women and their providers to consider bone density when comparing the plusses and minuses of Depo-Provera. "Although bone loss is one consideration, an unintended pregnancy has huge consequences in a woman’s life as well," she added.

Scholes advised that the following steps may help women improve or maintain bone health, whether they are using Depo-Provera or not:

• Get plenty of calcium
• Participate in weight-bearing exercise
• Don’t smoke
• Limit consumption of caffeinated beverages and sodas

How the study was conducted
Scholes and her colleagues compared hip and spine bone density measurements from 440 women, ages 18 to 39, who were enrolled in Group Health Cooperative, a Seattle-based health plan. A total of 182 participants were receiving Depo-Provera injections and 258 comparable women were not. Bone density measurements were taken at the start of the study, and at six-month intervals over the next three years.

Compared to non-users, Depo-Provera users had greater decreases in average bone density throughout the follow-up period. Women who used Depo-Provera continuously experienced a loss of bone density at the hip of 1.12 percent per year compared with 0.05 percent per year among non-users. Women who discontinued the use of Depo-Provera during the course of the study showed marked increases in bone density after discontinuation, although they recovered bone density at the hip more slowly than at the spine. By approximately 30 months after stopping Depo-Provera, bone density values for most Depo-Provera users were similar to those of non-users.

Funded by an $870,000 grant from the National Institute of Child Health and Human Development, the study was conducted by scientists from Group Health Center for Health Studies, the University of Washington’s Departments of Epidemiology and Biostatistics, and UW’s School of Medicine.

Although this project is complete, the researchers are continuing to study the effects of Depo-Provera injections and other risk factors on bone density in adolescent women.

About Group Health Center for Health Studies
Group Health Center for Health Studies conducts epidemiologic, health-services, and clinical research related to prevention, diagnosis, and treatment of major health problems. Funded primarily through government and private research grants, the Center is located in Seattle, Washington.

Group Health Cooperative is the nation’s largest consumer governed health care system, serving nearly 600,000 people in Washington and Idaho.

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