Purpose: The present study assesses the association between reproduction and hip fractures.
Methods: We used two surveys on elderly Danish twins of both sexes and the Danish National Register of Patients. In a cross-sectional study of 2045 twins aged 75-98 years in 1995, we studied the association between different aspects of reproduction and hip fractures leading to hospitalization between 1977 and 1994. In a prospective study, 3057 twins aged 66-99 years in 1977 were followed for a total of 29,112 years, and the association between number of children and incidence of hip fractures was investigated.
Results: In the cross-sectional study, as well as the prospective study, we found, for both sexes, that having no children was associated with a higher risk of hip fracture compared to having at least one child. When excluding persons without children, we found no effect of number of birth events/children. In the cross-sectional study, we found no effect of birth interval length or age at first birth. For women, we found an effect of age at last birth.
Conclusions: No "cost-of-reproduction" in terms of hip fractures was observed. On the contrary, we found that having one or more children was associated with a lower risk of hip fracture.