Serum free estradiol and estrogen receptor-α mediated activity are related to decreased incident hip fractures in older women

► Lack of population studies on serum estrogens and hip fracture risk in Asian women. ► We examine associations between estrogenic biomarkers hip fracture risk. ► High levels of free estradiol were associated with reduced hip fracture risk. ► ERα-mediated estrogen activity of serum was also associated with reduced hip fracture risk.