Relation of early menarche to high bone mineral density.

The study of background factors in individuals with high bone mineral density (BMD) may provide useful information in the prevention of osteoporosis. We investigated the relationship of reproductive factors to BMD. In 519 female volunteers (327 postmenopausal and 192 premenopausal women) ranging in age from 21 to 74 (mean 52.3 +/- 11.8) years, spinal BMD values were obtained using both quantitative computed tomography and dual x-ray absorptiometry. The z score was calculated from the mean BMD in each 5-year age group, and high BMD and low BMD was defined as BMD with z score > + 1.5 and < -1.5, respectively. Normal BMD was defined as BMD within the range - 1.0 < z score < +1.0. Long reproductive period, early menarche, and late menopause were associated with high BMD. Among these, the reproductive period showed the strongest association with BMD. In postmenopausal women, early menopause had a significant relationship with low BMD, and early menarche also had some relation to high BMD. In premenopausal women, there was a significant relationship between early menarche and high BMD. The age at menarche may have a strong association with peak bone mass, as suggested by the positive correlation of early menarche with high BMD observed in this study. It is considered important to prevent risk factors that disturb the beginning of menstruation in adolescent girls.