Reproductive factors as predictors of bone density and fractures in women at the age of 70.

The importance of reproductive and other health and social factors as predictors of bone mineral density (BMD) and fractures was investigated in a longitudinal study of 70-year-old women. At 70 years of age there was no correlation between menarcheal age, menopausal age, duration of fertile period and parity and BMD or a history of fractures. Bilateral oophorectomy (mean age at surgery 45.3 +/- 3.6 years) and the duration of tobacco smoking were negatively correlated to BMD at 70 years of age. Tobacco smoking was positively correlated to a history of fractures and body mass index (BMI) was negatively correlated to a history of fractures at 70 years of age. In a stepwise multiple regression model, height, body mass index and a history of hysterectomy were found to have a contributory, positively-correlated independent explanatory value for BMD at 70 years. In a logistic multiple regression analysis, bilateral oophorectomy was the only independent explanatory factor for fractures at 70 years of age. BMD was lower in women who had undergone bilateral oophorectomy compared with controls at 70 years of age. Hysterectomized women without bilateral oophorectomy showed a higher BMD in the right calcaneus at 70 years of age compared with controls. When comparing the reduction in bone mineral density between 70 and 76 years of age, the fifth quintile (women with the highest BMD) at 70 years of age decreased 2.7 times more (P < 0.01) than the first quintile. A longitudinal examination between 70 and 76 years revealed that BMD at the age of 70 was a significant (P < 0.01) predictor for fractures occurring between 70 and 76 years of age.