The aim of this study was to examine the relationships between oral contraceptive use and bone mineral density at the hip and spine. Community based women aged 41-76 years (n = 841) were recruited from four general practices in Cambridge. Each subject completed a health questionnaire. Spine (L2-L4, n = 841) and hip (n = 833) bone mineral density were measured by dual energy X-ray absorptiometry using the Hologic QDR-1000. After adjustment for age, there was no significant difference in regional bone mineral density between ever and never users of oral contraceptives. Similar results were obtained after stratifying for potential confounding factors including menopausal status, parity, smoking, hormone replacement therapy use, and body mass index. There was no relationship between duration of oral contraceptive use and bone mineral density. These results suggest that there is no relationship between oral contraceptive use and bone mineral density at the hip and spine in middle-aged women.
PIP: In England, 841 women aged 41-76 years who had attended 4 general practices in Cambridge participated in a study examining the effect of oral contraceptive (OC) use on bone mineral density. Dual energy x-ray absorptiometry (Hologic QDR-1000) was used to measure bone mineral density of the spine and hip (neck, trochanter, intertrochanteric region, and Ward's triangle). 42% of the women who had ever used OCs for a range of 1 to 312 months. Pre-/peri-menopausal women were more likely to have ever used OCs than postmenopausal women (69% vs. 31%; p 0.00001). Mean regional bone mineral density was much higher in ever users of OCs (p 0.00001), but the older age distribution of never users accounted for all of this effect. The researchers conducted multiple linear regression analyses while controlling for age, body mass index, current smoking status, menopausal status, gravidity, history of breast feeding, hormone replacement therapy, current alcohol intake, and current physical activity. They found that ever use of OCs had no effect on bone mass in the hip and spine. Further, the researchers also learned that no significant difference in bone mineral density existed between never users and women who had used OCs for the longest duration. Strengths of the study were large sample size, a large number of postmenopausal women, and use of a community-based sample of women. The lack of information on dosage did not allow the researchers to examine any potential dose-response relationships. These findings indicated that no relationship exists between OC use and bone mineral density in the hip and spine in middle-aged women.