Tubal sterilization and risk of breast cancer mortality in US women.

Objective: To investigate the hypothesis that tubal sterilization is associated with a reduced risk of breast cancer.
Methods: We examined this hypothesis in a large prospective study of US adults. After 14 years of mortality follow-up, 3837 deaths from breast cancer were observed in a cohort of 619,199 women who were cancer-free at study entry in 1982.
Results: Cox proportional hazards models (adjusted for multiple breast cancer risk factors) showed a significant inverse association between tubal sterilization and breast cancer mortality (adjusted rate ratio (RR) = 0.82, 95% confidence interval (CI) 0.70-0.96). Women who were sterilized before age 35 had a lower risk (adjusted RR = 0.69, 95% CI 0.53-0.88) than women who were sterilized at 35 years of age or older (adjusted RR = 0.92, 95% CI 0.75-1.13). Also, sterilizations performed before 1975 resulted in a lower risk (RR = 0.75, 95% CI 0.62-0.91) than those performed during or after 1975 (RR = 0.98, 95% CI 0.74-1.29), possibly reflecting the likelihood of greater tissue damage with earlier procedures.
Conclusions: These results suggest that tubal sterilization may lower subsequent risk of breast cancer, especially among women who are sterilized at a relatively young age. Additional studies are needed to confirm or refute these findings.