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The Pill & bone health: New study eyes impact
Revamp your oral contraceptive (OC) counseling: Results of a new study indicate that Pill use is not associated with an increase or a decrease in fracture risk.1
Two earlier investigations had shown an increased fracture risk in premenopausal women who used the Pill, explains Peter Vestergaard, MD, PhD, lead author of the research and senior registrar in the Department of Endocrinology and Metabolism at Aarhus (Denmark) University Hospital.2,3 "The reason why we wanted to investigate this was that oral contraceptives are in widespread use, and that prior studies had indicated that oral contraceptives could be associated with an increase in fracture risk," he explains. "Even though the increase was small, a large number of fractures could thus theoretically be the result of oral contraceptives."
According to Vestergaard, the two prior studies were based on the same prescription register and did not adjust for a number of important factors. The Danish researchers had access to a large national register that could help to better determine if oral contraceptives were associated with fracture risk, he explains.
Danish researchers selected all women with a fracture (64,548) in the year 2000 in Denmark from the National Hospital Discharge Register to serve as cases in the study. For each case, three age-matched controls were randomly drawn from the general population. Exposure was use of OCs between Jan. 1, 1996, and Dec. 31, 2000. Adjustments were made for use of other drugs, pregnancy, prior fracture, other diseases and social variables.
In the unadjusted analysis, use of OCs in low dose was associated with a small increase in overall fracture risk. However, upon adjustment, no increase in fracture risk could be demonstrated in any age or dose group.1
Although researchers adjusted for several potential confounding factors in the statistical analyses, they note that results still may be influenced by potential confounding factors not included in the analyses, such as smoking, physical activity, differences in body weight, and use of calcium/vitamin D supplements.1
OCs for bone health?
Decline in bone density in women normally starts between the ages of 30 and 40; OCs may counter this demineralization.4 According to one review of the literature, evidence suggests that premenopausal use of OCs is beneficial for preserving bone mass.5 While researchers have not yet determined the optimal estrogen dosage, "it appears that in the premenopausal woman, oral contraceptives that will provide bone-sparing effects while minimizing long-term complications should contain the equivalent of ≥ 20 mcg/day," the review states.5
One analysis indicates that exposure to the estrogen from OCs during the premenopausal years may have a small beneficial effect on the skeleton in white women.6
Female athletes may experience loss of menses, low bone mass, and an increased frequency of stress fractures due to intense physical activity. Researchers are conducting a study to see if use of OCs reduce stress fracture incidence and prevent loss of bone mass or increase bone mass among highly trained female athletes.
Low serum estrogen levels are believed to be a principal cause of bone loss in highly trained female athletes. If so, re-establishing normal estrogen levels in these women should prevent or retard bone loss and decrease the incidence of stress fractures, researchers believe.
Data collection for the study has been completed, says Kristin Cobb, PhD, lead investigator for the study and clinical assistant professor in the health research & policy-epidemiology department at the Stanford (CA) University School of Medicine. Results are being analyzed, she says. (Editor's note: CTU will report on the data upon publication.)