Use research to minimize bone loss in DMPA users

Findings from a new study identify women at higher risk of significant bone loss on injectable birth control.1 The study, conducted by researchers at the University of Texas Medical Branch at Galveston over two years, followed 95 users of DMPA (depot medroxyprogesterone acetate; Depo-Provera, Pfizer, New York City; Medroxyprogesterone Acetate Injectable Suspension; USP, Teva Pharmaceuticals USA, North Wales, PA). In that time, 45 women had at least 5% bone mineral density (BMD) loss in the lower back or hip. Fifty women had less than 5% bone loss at both sites during the same period.

Using logistic regression analysis to examine predictive factors, researchers determined that women who have not delivered a child, smoke, and do not consume much calcium in their diet are at risk for higher bone loss while using DMPA. These women require additional counseling on how to decrease their risk of BMD loss to avoid putting their bone health at risk. The risk of higher BMD loss associated with DMPA use might be reduced by quitting smoking and increasing calcium intake; having had a child is also protective, researchers conclude.1

This study reports that BMD loss is not a significant concern for all women who choose DMPA for contraception because it is associated with certain risk factors. Those who had delivered a child, did not smoke, and consumed at least 600 mg a day of calcium did not lose more than 2% of their BMD at the spine or hip over 24 months. Thus, concerns about their bone health are minimal, the paper states. 1

"Bone mineral density loss is not a significant concern for all women who choose DMPA," says senior author Abbey Berenson, MD, MMS, professor in the Department of Obstetrics and Gynecology and director of the Center for Interdisciplinary Research in Women's Health at the university. "Based on these findings, clinicians have the information they need to recommend basic behavior changes for high-risk women to minimize BMD loss."

DMPA continues as a top choice for birth control, particularly for adolescents, say respondents to the 2009 Contraceptive Technology Update Contraception Survey.

In the current study, findings indicate BMD loss was higher in women who were current smokers, had never given birth, and had a daily calcium intake of 600 mg or less. The National Institutes of Health recommends that women ages 14-18 have a daily intake of 1,300 mg of calcium per day to maintain bone health, with 1,000 mg recommended for women ages 19-50. 2

Researchers report BMD loss substantially increased among the women with all three risk factors. Age, race, ethnicity, previous contraceptive use, and body mass index were not associated with higher BMD loss, they found.

Twenty-seven women were followed for an additional year. Researchers found that those who experienced significant BMD loss in the first two years continued to lose bone mass. Co-author Mahbubur Rahman, MD, PhD, MPH, assistant professor in the Department of Obstetrics and Gynecology and Center for Interdisciplinary Research in Women's Health, says, "These losses, especially among women using DMPA for many years, are likely to take an extended period of time to reverse."

What can you do?

What Are Good Sources of CalciumWhat can you do to help women preserve their bone health? Researchers in the current study reported that about 8.9% of the women using DMPA took calcium supplements at least four days a week, demonstrating that few young women of reproductive age understand the importance of adequate calcium consumption. (The National Institute of Arthritis and Musculoskeletal and Skin Diseases offers an easy-to-read, freely downloadable handout at its site, www.niams.nih.gov. Under "Health Information Index," select "B," then "Bone Health and Diseases," and "Bone Health." Under "Related Information," select "Bone Health for Life." Also see the box item for sources of dietary calcium, left.)

Also, take the opportunity to discuss smoking cessation programs in your area when counseling patients, researchers suggest. Review available medications that can assist with patients' efforts to quit. (The National Cancer Institute offers freely downloadable information sheets at its web site, www.cancer.gov. Under "Cancer Topics," select "Prevention, Genetics, Causes," then "Smoking Home Page," then "Quitting Tobacco: Challenges, Strategies, and Benefits." Select from such topics as "Why to Quit and How to Get Help" and "Enjoying Meals . . . Without Smoking.")

Prevention of bone loss while using DMPA is not well understood and remains an important topic for future research, say the authors of the current study. Research has examined using estrogen supplementation. For example, in a double-blind, placebo-controlled trial in women with a mean age of 37 years, findings suggest such supplementation can result in a 1% increase in spinal BMD per year among users of DMPA as compared with a 2.6% loss annually among those who did not take estrogen.3 While such research suggests that low-dose estrogen supplementation can slow bone DMPA bone loss, the American College of Obstetricians and Gynecologists does not recommend such practice.4

References

  1. Rahman M, Berenson AB. Predictors of higher bone mineral density loss and use of depot medroxyprogesterone acetate. Obstet Gynecol 2010; 115:35-40.
  2. National Institutes of Health, Office of Dietary Supplements. Dietary Supplement Fact Sheet: Calcium. Accessed at ods.od.nih.gov/factsheets/calcium.asp.
  3. Cundy T, Ames R, Horne A, et al. A randomized controlled trial of estrogen replacement therapy in long-term users of depot medroxyprogesterone acetate. J Clin Endocrinol Metab 2003; 88:78-81.
  4. ACOG Committee Opinion No. 415: Depot Medroxypro-gesterone Acetate and Bone Effects. Obstet Gynecol 2008; 112: 727-730.