Bone loss in DMPA users mostly reversible

Add just-published research to your counseling on Depo-Provera (depot medroxyprogesterone acetate or DMPA): Use of the injectable contraceptive is strongly associated with bone density loss; however bone loss appears to be largely reversible once the injections are stopped.1

Loss of bone density increases the risk for osteoporosis, a disease in which bones become fragile and are more likely to break. The new study findings indicate that women who used DMPA continuously for three years experienced about the same amount of bone loss as women who are breast-feeding or going through menopause. While the new research shows that the bone loss is largely reversible, providers should discuss the issue during contraceptive counseling with women with risk factors for osteoporosis, according to the Bethesda, MD-based National Institute of Child Health and Human Development (NICHD), which funded the research. Risk factors for osteoporosis include smoking, thin or small frame, prior broken bones, Caucasian or Asian ancestry, family history of osteoporosis, and diet low in calcium.

Since DMPA reduces estrogen levels, the study was proposed in 1993 in response to previous findings associating hypoestrogenic conditions with decreased bone density, as well as preliminary results suggesting that long-term DMPA users had lower bone density than nonusers,2 states Steven Kaufman, MD, MS, a medical officer in the Contraception and Reproductive Health Branch of the NICHD.

"The method’s popularity — it was being used at that time by more than 3.5 million women worldwide and had recently been licensed for use in the U.S. — made this an important question of potentially high public health significance," says Kaufman.

Since the Food and Drug Administration approved the method in 1992, use of DMPA, marketed in the U.S. by Pharmacia Corp. in Peapack, NJ, has grown among adolescent users. While about half of teens report use of OCs, and a third say they use condoms, about 10% record use of DMPA.3

To get a more in-depth look at the effect of DMPA in adolescents, researchers are continuing to study the effects of DMPA injections and other risk factors on bone density in this population, says Delia Scholes, PhD, associate scientific investigator with the Center for Health Studies at the Seattle-based Group Health Cooperative of Puget Sound and lead author of the current study. Investigators are completing 24-month follow-up visits for the adolescent prospective cohort study, she reports.

"The project will be completed early in 2003, and we will have 24-36 months of longitudinal follow-up on a group of 174 teens between the ages of 14 and 18," states Scholes. "Eighty-one of our participants were using DMPA, and 93 were not [our comparison group]."

For the just-published study, Scholes and her colleagues compared hip and spine bone density measurements from 440 women, ages 18-39, who were enrolled in Group Health Cooperative, a Seattle-based health plan. A total of 182 participants were using DMPA, 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 nonusers, DMPA users had greater decreases in average bone density throughout the follow-up period. Women who used the contraceptive injection continuously experienced a loss of bone density at the hip of 1.12% per year compared with 0.05% per year among nonusers. Women who discontinued DMPA 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 DMPA, bone density values for most DMPA users were similar to those of nonusers.

The only exception occurred among women between the ages of 18 and 21, whose bone density values continued to lag behind those of non-users even 2½ years after stopping Depo-Provera. The authors of the study attribute this finding to the 18-21 year-old users’ large bone density deficits at the beginning of the study.

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

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

  • obtain plenty of calcium;
  • participate in weight-bearing exercise;
  • don’t smoke;
  • limit consumption of caffeinated beverages and sodas.

Choosing a contraceptive involves a highly individualized set of decisions, observes Scholes. 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," notes Scholes.

References

1. Scholes D, LaCroix AZ, Ichikawa LE, et al. Injectable hormone contraception and bone density: Results from a prospective study. Epidemiology 2002; 13:581-587.

2. Cundy T, Evans M, Roberts H, et al. Bone density in women receiving depot medroxyprogesterone acetate for contraception. BMJ 1991; 303:13-16.

3. Abma JC, Chandra A, Mosher WD, et al. Fertility, family planning, and women’s health New data from the 1995 National Survey of Family Growth. Vital Health Stat 1997; Series 23(19).