Menstrual history and risk of hip fractures in postmenopausal women. The Iowa Women's Health Study.

The authors examined prospectively between 1986 and 1997 the relation of irregular menstrual cycles and irregular menstrual bleeding duration earlier in life with risk of hip fracture in 33,434 postmenopausal Iowa women. Over the 318,522 person-years of follow-up, 523 hip fractures were reported. Adjusted for age, smoking, body mass index, waist/hip ratio, and estrogen use, the relative risk of hip fracture in women who reported always having irregular menstrual cycles, compared with women who never had irregular cycles, was 1.36 (95% confidence interval (CI): 1.03, 1.78). Women who reported having irregular menstrual bleeding duration had a 1.40-fold (95% CI: 1.10, 1.78) increased risk of hip fracture compared with women with regular bleeding duration. In addition, women who reported having both irregular menstrual cycles and irregular menstrual bleeding had a 1.82-fold (95% CI: 1.55, 2.15) higher risk of hip fracture than did women who reported neither irregularity. Women who reported only one menstrual disturbance did not have a risk of hip fracture that was significantly different from women who reported no menstrual disturbances. The authors conclude that women with menstrual irregularities are at increased risk of hip fracture, probably because they are estrogen or progesterone deficient.