Oral contraceptive use increases bone density and lower the risk of osteoporosis

Introduction: Osteoporotic fractures are one of the leading causes of disability in older women. Decreased bone mineral density (BMD) due to reduced estrogen levels after menopause is a primary risk factor. The use of oral contraceptive pills (OCP) containing exogenous estrogen is widespread, yet their long-term effects on bone health later in life remain unclear. Here, we therefore assess the impact of OCP use on BMD and the risk of osteoporosis. Methods: We included 257,185 women from the UK Biobank cohort, born between 1936 and 1970. Using a prospective study design, we estimated the effect of OCP use on osteoporosis through time-dependent Cox regression. BMD, measured as T score based on quantitative ultrasound of the calcaneus, was assessed at recruitment to the UK Biobank. We applied multivariable linear regression to estimate the effect of prior OCP use on BMD. Results: As much as 7.6 % of the participants received an osteoporosis diagnose until the end of follow up in 2020. The risk of osteoporosis was lower among ever OCP users, hazard ratio: 0.86 (95% CI 0.83-0.89). OCP use also resulted in a higher BMD (0.052, 95% CI 0.038-0.067) an effect that increased with longer OCP use. Discussion: We have demonstrated that previous OCP use is associated with higher BMD and a reduced risk of osteoporosis with long-lasting effects. These findings suggest that OCP use should be considered an important factor in potentially reducing the risk of osteoporotic complications in older women.