The adverse effect on bone mineral density (BMD) of depot medroxyprogesterone acetate (DMPA) is a concern and studies have not been able to determine who is at greatest risk of losing more BMD while using DMPA. This study aimed to identify possible predictive factors of higher bone loss, defined as at least 5%, at the spine or femoral neck over time in DMPA users.

This study was part of a larger study of 805 non-Hispanic African-American, non-Hispanic White and Hispanic women aged between 16 and 33 years. This analyses focused only on the DMPA users (n = 240, mean age 23.8 years). BMD was measured at the lumbar spine and femoral neck every 6 months. Of the 240 initial users, 145 discontinued DMPA, leaving 95 completing 24 months of follow-up. The study found that 45 (47.4%) of women had at least 5% BMD loss at the lumbar spine or femoral neck by 24 months and the multivariable logistic regression model showed that this was associated with:

• Current smoking (adjusted odds ratio 3.88; 95% CI, 1.26 to 11.96)

• Calcium intake (0.81; 0.65 to 0.99)

• Parity (0.49; 0.29 to 0.82)

Age, race or ethnicity, previous contraceptive use, and BMI were not associated with higher BMD loss.

The researchers conclude from these findings 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 counselling on how to decrease their risk of BMD loss to avoid putting their bone health at risk.” They acknowledge that these findings are limited by the small sample size, recall bias of data such as calcium intake and amount of exercise, and high discontinuation rate.” In addition, there were insufficient women in the “at least 5% bone loss” group followed after DMPA discontinuation to examine the reversibility of these findings among this subset.