Combined hormonal contraceptives use and bone mineral density changes in adolescent and young women in a prospective population-based Canada-wide observational study.

OBJECTIVES

To assess combined hormonal contraceptives (CHC) use and adolescent women's peak areal bone mineral density (BMD) accrual.

METHODS

We enrolled 527 randomly selected women across Canada (2004-6) divided by age into adolescents (16-19) and young adults (20-24) and by CHC use to ever (E-CHC)/never (N-CHC) users. At baseline and year 2 we measured height, weight, and BMD at lumbar spine (L1-4), femoral neck, and total hip sites. Interviewer-administered questionnaires addressed menarche age, cigarette and alcohol use, calcium/vitamin D intakes, physical activity and estrogen dose (≤30/>30 micrograms). Linear regression models examined associations of CHC use with 2-year BMD change adjusted for bone-related variables.

RESULTS

Of 307 women with complete data, 229 (75%) used CHC. N-CHC adolescents gained significantly more unadjusted total hip BMD +0.012 g/cm/2-y (95% C.I.: 0.001, 0.023) with similar trends at all sites. N-CHC adolescents tended to have greater adjusted femoral neck BMD gain: mean difference +0.009 g/cm (95% CI: -0.002; 0.021). In young women N-CHC, however, adjusted femoral neck BMD decreased significantly more -0.021 g/cm (95%CI: -0.006; -0.036) with similar trends at other sites. BMD changes were unrelated to estrogen dose and age at starting CHC.

CONCLUSIONS

Adolescent CHC users in a random population demonstrated less hip region peak BMD accrual than non-users. This requires randomized control trial confirmation.