Reproductive factors and fatal hip fractures. A Norwegian prospective study of 63,000 women.

STUDY OBJECTIVE The aim of the study was to investigate the impact of reproductive variables (age at menarche, menopause, first and last birth as well as parity, lactation, and abortions) on hip fracture mortality. DESIGN AND SETTING A prospective study in Norway with more than 60,000 women followed up for 29 years. A total of 465 deaths as a result of hip fracture were recorded. MAIN RESULTS Statistically significant linear relations (p < or = 0.02) were found between both age at menarche and length of reproductive period (defined as age at menopause to age at menarche) and the mortality of hip fractures in women aged less than 80. The death rate for women with a late menarche (> or = 17 years) was twice that of the women with relatively early menarche (< or = 13 years). Compared with women with less than 30 years between menopause and menarche, the mortality rate ratio in women with more than 38 reproductive years was 0.5. We also found an inverse relation with age at first birth. CONCLUSIONS This study supports by hypothesis that an early menarche and a long reproductive period protect against hip fracture mortality. High age at first birth may also be protective.