THE EFFECT OF PREVIOUS ORAL-CONTRACEPTIVE USE ON BONE-MINERAL DENSITYIN PERIMENOPAUSAL WOMEN

The bone mineral density (BMD) of the lumbar vertebrae L2-4 and femora l neck was determined by dual-energy X-ray absorptiometry (DXA) in 322 2 perimenopausal women - a random stratified sample of the population- based Kuopio Osteoporosis Study (OSTPRE). The mean age of the women wa s 53.4 years (range 47.9-59.6 years). Twenty-nine percent of the women were past users of oral contraceptives (OC) containing 50 mug or less of ethinyl estradiol and 7.4% (n = 250) of the women reported OC use for more than 6 years. There was a slight but statistically significan t difference between OC users (n = 939) and non-users (n = 2283) in lu mbar BMD (1.134 +/- 0.155 g/cm2 v 1.123 +/- 0.161 g/cm2, p = 0.014). A statistically significant difference was recorded also after adjustme nt for years since menopause, duration of hormonal replacement therapy (HRT) and present weight (p = 0.044). When the analysis was performed among women who had never used oestrogen replacement therapy (n = 142 7) and among premenopausal women (n = 387), no differences in BMD were found between OC users and non-users. Similarly, femoral neck BMD did not differ between the groups. This population-based study demonstrat ed a slightly higher lumbar BMD among past OC users. However, OC users and non-users differed from each other in many behavioral characteris tics. Thus, the differences in BMD may be accounted for more by other factors than by past OC use itself. The low-dosage estrogen OCs used t oday would not be expected to have any positive bone effects among fut ure perimenopausal women.