To test the hypothesis that osteoporosis, which results partly from long-te
rm estrogen deficiency, is associated with a lowered risk of breast cancer,
a population-based cohort study was performed in Amiens. To ascertain the
incidence of breast cancer, 1300 women were followed through after a first
hip fracture. Overall, 18 cases of cancer were observed cf. 21.8 expected (
standardized incidence ratio (SIR): 0.82; 95% confidence interval (CI): 0.5
-1.3). The results are consistent with previous studies which concluded tha
t long-term estrogen deficiency is associated with a reduced risk of develo
ping breast cancer.