Oral-contraceptive use and risk of hip fracture: a case-control study

Background Epidemiological studies indicate a protective effect of postmeno pausal oestrogen therapy on the risk of osteoporotic fractures. Whether pre menopausal oestrogen exposure in the form of oral contraceptives also reduc es the risk of osteoporotic fractures remains uncertain. Method We did a population-based case control study of hip fracture among S wedish postmenopausal women, 50-81 years of age, through mailed questionnai res and telephone interviews. Of those women who were eligible, 1327 (82.5% ) cases and 3312 (81.6%) randomly selected controls responded. Findings 130 (11.6%) cases and 562 (19.1%) controls reported ever-use of or al contraceptives. Ever-use of oral contraceptives was associated with a 25 % reduction in hip fracture risk (odds ratio 0.75 [95% CI 0.59-0.96]). Wome n who had ever used a high-dose pill (equivalent to greater than or equal t o 50 pg ethinylestradiol per tablet) had a 44% lower risk for hip fracture than never-users (0.56 [0.42-0.75]). No overall trend was observed with dur ation of oral-contraceptive use, or time since last use. However, when maki ng comparisons with women who have never used oral contraceptives, the odds ratios for hip-fracture were 0.69 (0.51-0.94) for use after age 40, 0.82 ( 0.57-1.16) for use at ages 30-39, and 1.26 (0.76-2.09) for use before age 3 0. Interpretation Our results imply that in postmenopausal women, oral-contrac eptive use late in reproductive life may reduce the risk of hip fracture, a lthough we recognise the limitations of the case-control method.