Oral contraceptive use in young women is associated with lower bone mineral density than that of controls

Osteoporosis is a skeletal disease affecting 44 million Americans. A primary strategy to prevent osteoporosis is to develop a high peak bone mass in youth. Oral contraceptives (OCs) alter hormones in women and could affect bone mass development. Fifty percent of American women between the ages of 20 and 24 years use OCs. However, the interaction between OCs and skeletal mineralization is poorly understood. Our aim was to compare bone mass [bone mineral density (BMD)] of young women who had a history of OC use, with regularly menstruating controls. We recruited 98 women who were 18 to 25 years of age and had a history of OC use (n=44, 3.4 +/- 1.9 years of OC use) and controls (n=58). BMD at the hip, whole-body, and spine [anterior-posterior (AP) and lateral grams per square centimeter] was measured by dual-energy X-ray absorptiometry (DXA). Physical activity [in metabolic equivalents (METs)] was measured via questionnaire, and grip strength was evaluated with an isometric dynamometer. Groups were similar in body mass index (BMI), fat mass, grip strength, calcium intake and physical activity, but OC users were slightly older than controls (21.3 +/- 1.9 years vs 20.3 +/- 1.6 years, P < 0.05). In analysis of covariance, controlled for age and BMI, controls had significantly greater BMD than OC users at the AP and lateral spine, femoral neck, greater trochanter, total hip, and whole body (P < 0.05). We conclude that, in this cross-sectional analysis, oral contraceptive use by young women may compromise bone health during a time when mineral is still accruing.