A cross-sectional study of the forearm bone mineral density in long-term current users of the injectable contraceptive depot medroxyprogesterone acetate.

BACKGROUND: One of the well-established effects of the use of depot medroxyprogesterone acetate (DMPA) contraception is on bone mineral density (BMD). However, little evidence assesses the skeletal impact of long-term DMPA use. The objective of this study was to assess BMD on a cohort of women who used DMPA uninterruptedly between 1 and 15 years.

STUDY DESIGN: A cross-sectional study with 232 users of DMPA matched to a group of 232 copper intrauterine device (IUD) users by age (±1) (range 20-53 and 20-51 years for DMPA and IUD group, respectively), body mass index (BMI; kg/m(2)) (±1) (range 17.4-44.5 and 18.5-40.2 for DMPA and IUD group, respectively) and years of use (1-15 years) was performed. The women underwent forearm BMD evaluation using dual-energy X-ray absorptiometry. The women were divided into five groups (1-5) according to the length of DMPA use: 1-3, 4-6, 7-9, 10-12 and 13-15 years of use.

RESULTS: The mean (±SEM) age was 38.3±0.5 and 38.1±0.57 years and the mean (±SEM) BMI (kg/m(2)) was 26.4±0.3 and 26.3±0.3 for the entire group of women in the DMPA and IUD group, respectively. Women who used DMPA or IUD for a short time were younger and had lower BMI (kg/m(2)) than the women who used either contraceptive method long term. White women were significantly more frequent among IUD users (p<.040) than DMPA users. In addition, parity (p<.053) and physical activity (p<.012) were significantly greater among IUD users, whereas the prevalence of washing clothes by hand (p<.025) was significantly greater among DMPA users. There was no significant difference in BMD measurements between the current users of DMPA and those who had used the IUD either at the distal or ultra-distal sections of the forearm. However, women who had used DMPA for 13-15 years showed significantly lower BMD at the distal and ultra-distal radius when compared to IUD users (p<.041 and .042, respectively). Otherwise, all other differences in BMD values between DMPA and IUD users were nonsignificant at the distal and ultra-distal radius. For both DMPA and IUD users, we noted a direct correlation between higher BMD and BMI (kg/m(2)) and an inverse correlation between BMD and age for distal and ultra-distal radius.

CONCLUSIONS: Our study did not detect a deleterious effect on measurements of forearm BMD among long-term DMPA users with less than 13 years of use; however, a significantly lower BMD was observed at 13-15 years of use in DMPA users when compared to IUD users. Bone mineral density was inversely correlated to older age and directly correlated to BMI (kg/m(2)).