Peng K, Yao P, Yang L, et al. - This study was attempted to correlate the relationships of number of children with risk of hip fracture between men and women aged over 50 years. Between 2004 and 2008, the China Kadoorie Biobank (CKB) included 133,399 women and 110,296 men, aged 50 years or older. In this study, 2,068 participants (1394 women and 674 men) suffered a hip fracture during 10-year follow-up. Researchers calculated sex-specific adjusted hazard ratios (HRs) and 95% CI for incident hip fracture using cox regression analysis. The results of this study showed that concordant effects of the number of children with risk of hip fracture between men and women demonstrate that the lower risks in multiparous women are not due to differences in oestrogen exposure or other biological impact, but may reflect residual confounding by socioeconomic or lifestyle factors.