Abstract
SummaryThis prospective study of Chinese adults demonstrated an inverse J-shaped association of number of children with risk of hip fracture in both men and postmenopausal women aged 50 years or older. Women with 2 or 3 children and men with 4 children had the lowest risk of hip fracture.IntroductionWomen have higher absolute risks of fracture than men, which is believed to reflect differences in oestrogen exposure. The aim of this study was to compare the associations of number of children with risk of hip fracture between men and women aged over 50 years.MethodsThe China Kadoorie Biobank (CKB) recruited 133,399 women and 110,296 men, aged 50 years or older between 2004 and 2008. During 10-year follow-up, 2068 participants (1394 women and 674 men) suffered a hip fracture. Cox regression analysis was used to estimate sex-specific adjusted hazard ratios (HRs) and 95% CI for incident hip fracture.ResultsOver 98% of both subsets of men and women aged 50 or older reported having children. Women who had 2 or 3 children had the lowest risks of hip fracture compared with other groups. Compared with nulliparous women, the adjusted HR for hip fracture were 0.89 (95% CI; 0.72, 1.10) for 1 child, 0.79 (0.70, 0.90) for 2 children, 0.79 (0.72, 0.87) for 3 children, 0.81 (0.72, 0.91) for 4 children, and 0.95 (0.83, 1.10) for those with 5 or more children. The associations of number of children with hip fracture were broadly consistent in men of a similar age.ConclusionsThe concordant effects of the number of children with risk of hip fracture between men and women suggest that the lower risks in multiparous women are not due to differences in oestrogen exposure or other biological effects, but may reflect residual confounding by socioeconomic or lifestyle factors.
Highlights
Hip fracture is a major public health problem associated with a high morbidity and mortality in both developed and developing countries
We examined the associations of number of children with risk of incident hip fracture in both older women and men in the China Kadoorie Biobank (CKB)
Nulliparous women tended to have a higher risk of hip fracture compared with parous women in Number of children
Summary
Hip fracture is a major public health problem associated with a high morbidity and mortality in both developed and developing countries. It has been estimated that about 50% of all hip fractures will occur in Asian populations by 2050 [1,2,3,4]. Women start to suffer bone loss between 30 and 39 years, and their risks of fracture increase substantially after the menopause. 1 in 3 women and 1 in 5 men over age 50 years will experience an osteoporotic fracture with hip fractures being the most serious type of fracture [5,6,7]. The number of biological children has been linked with higher risks of hip fracture [8,9,10,11,12].
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