The Pill May Decrease Bone Density

Jan. 16 -- FRIDAY, Jan. 15 (HealthDay News) -- Oral contraception may decrease bone density in young women, a new study suggests.

Those taking birth control pills for more than two years, and those on the low-dose estrogen pills appear to have the greatest risk of decreased bone density in the spine and whole body, according to the researchers.

"I think the evidence is still emerging on this association, but our findings suggest that low-dose oral contraceptives with long-term use have some impact on bone density," said study author Delia Scholes, a senior investigator at the Group Health Research Institute of Group Health Cooperative in Seattle.

The findings were published in the January issue of Contraception.

What isn't entirely clear from this study of women under 30, explained Scholes, is what the long-term impact might be. Researchers don't know if the lower bone density findings are easily reversible just by stopping the use of oral contraceptives. They also weren't able to study if the lower bone density in these young women would translate to a higher fracture risk later in life.

But, "if oral contraceptives are indeed causing the approximately 5 percent lower spine bone density for oral contraceptive users versus non-users that we observed in our study, and if that impact is not reversed with oral contraceptive discontinuation or with other factors that may occur across the life span, a 5 percent lower bone density after menopause is associated with approximately 50 percent more osteoporotic fractures," said Scholes.

Almost 12 million American women are currently using oral contraception, according to background information in the study. And, the use of oral contraception is highest in women under 30, reports the study. That's important because the 20s are generally a time of peak bone mass production.

However, little is known about the effects of oral contraception on bone density. Previous studies have had conflicting results, with some showing no effect or a benefit on bone density while others suggest that oral contraceptives may inhibit bone mass accrual.