Long-term restoration of deficits in bone mineral density is inadequate in premenopausal women with prior menstrual irregularity.

OBJECTIVE

To investigate change in bone mineral density (BMD) in premenopausal women (age, 29-46 years), some of whom were marathon runners with a history of menstrual irregularity.

DESIGN

Longitudinal follow-up.

SETTING

University medical school.

PARTICIPANTS

We investigated 8 sedentary controls (SC) and 19 marathon runners (12 with regular menses (R) and 7 with a history of irregularity (OA) 11.7 +/- 7.9 years before follow-up).

MAIN OUTCOME MEASURES

BMD (g/cm2) of lumbar spine (LS) and proximal femur were determined at baseline and follow-up (3-5 years later). We calculated a menstrual history index (MHI) (estimated periods/year since age 13).

RESULTS

Body mass, age at menarche, and femoral BMD were not statistically different. Follow-up LS BMD (g/cm2) was lower (p < 0.01) in OA (0.936 +/- 0.060) than in R (1.043 +/- 0.103) and SC (1.094 +/- 0.077), even when covarying for age or both age and mass. No group changed BMD significantly with time. Current MHI was lower (p < 0.001) in OA (9.7 +/- 1.4) than in R (11.3 +/- 0.5) and SC (11.8 +/- 0.4). MHI for the teenage years was lower in OA than in SC but not in R. OA had significantly lower MHI than did R and SC for the third and fourth decades. Only MHI during the third decade correlated significantly with LS BMD for all subjects.

CONCLUSIONS

Restoration of LS BMD deficit in women with prior menstrual irregularity aged over 30 is slow and may never reach the same level as age-related controls; secondly, this may be the result of both bone loss in the third decade of life and reduced acquisition during adolescence.