Hip fracture risk was assessed according to parity among postmenopausal women. Compared with nulliparous women, the fracture risk was lower in women with three or more births.
Introduction: Parity was assessed for long-term prediction of hip fracture in postmenopausal women.
Methods: Postmenopausal women (n= 2,028) aged 45 or over with no history of hip fracture were studied. From 1978 to 1980, all of them had participated in a comprehensive health survey based on a nationally representative population sample. Emerging cases of hip fracture were identified from the National Hospital Discharge Register during a follow-up period extending up to 17 years.
Results: The risk of hip fracture was lower among parous women compared with nulliparous women. The model adjusted for age showed a significant inverse association between parity as a continuous variable and the risk of hip fracture [RR = 0.74; 95% confidence interval (CI), 0.61-0.90] per an increment of one standard deviation (2.4 births). Adjusted for age, menopausal age, level of education, body mass index, vitamin D status, alcohol consumption, smoking history, leisure time physical activity, and self-rated health, the relative risk was 0.50 (95% CI, 0.32-0.79) for women with three or more births and 0.85 (95% CI, 0.55-1.32) for women with one to two births as compared with nulliparous women.
Conclusion: Parity, three or more births in particular, predicts a lowered risk of hip fracture in the long run.