Breastfeeding and other reproductive factors and the risk of hip fractures in elderly women.

The objective of this population-based case-control study was to clarify the relationships between parity, breastfeeding and ages at menarche and menopause and the risk of hip fracture among elderly women. The study base comprised women aged 65 years and over living in a defined region in Sydney, Australia, during 1990-1991. Cases (n = 174) were recruited from 12 hospitals and controls (n = 137) were selected using an area probability sampling method, with additional sampling from nursing homes. The age- and proxy-adjusted odds ratio (OR) comparing parous women who had never breastfed with nulliparous women was 2.11 (95% confidence interval (CI): 0.85-5.25). Among parous women, the age- and proxy-adjusted OR for ever versus never breastfeeding was 0.47 (95% CI: 0.22-0.99). There was a dose-response relationship between average duration of breastfeeding per child and risk of hip fracture (test for trend: P < 0.01). Age at menopause and age at menarche were only weakly associated with hip fracture risk. This study suggests that breastfeeding may protect parous women against hip fracture in old age.