Tubal ligation in relation to menopausal symptoms and breast cancer risk

Background: Local inflammation after tubal ligation may affect ovarian function and breast cancer risk. Methods: We analysed tubal ligation, menopausal characteristics, and breast cancer risk in the Sister Study cohort (N 50 884 women). Results: Tubal ligation was associated with hot flashes (hazard ratio (HR) 1.09; 95 % confidence interval (CI): 1.06–1.12) but not menopausal age (HR 0.99; 95 % CI: 0.96–1.02). Tubal ligation did not have an impact on breast cancer overall (HR 0.95; 95% CI: 0.85–1.06), but had a suggested inverse relation with oestrogen receptorþ /progesterone receptorþ invasive tumours (HR 0.84; 95 % CI: 0.70–1.01), possibly because of subsequent hysterectomy/bilateral oophorectomy. Conclusion: Tubal ligation does not influence overall breast cancer risk. The US Collaborative Review of Sterilization reported reduced menstrual bleeding and pain and increased cycle irregularity after tubal ligation (Peterson et al, 2000). These findings provided evidence against a ‘post-tubal ligation syndrome ’ that included dysmenorrhoea and menorrhagia, but could not address long-term outcomes, such as altered menopausal age (Pokoradi et al, 2011), symptoms (Whiteman et al, 2004; Wyshak, 2004; Nelson et al, 2005), or breast cancer risk. A recent meta-analysis reported no association between tubal ligation and breast cancer (RR 0.97); however, substantial heterogeneity between studies (I2 82.2%, Po0.001) was observed. Effect estimates among eight studies ranged from RR 0.37 (0.19, 0.68) to 1.20 (1.00, 1.30) (Gaudet et al, 2013). This variability may be partly due to incomplete information on subsequent gynaecologic surgeries and tumour subtypes. Women who have a tubal ligation are more likely to undergo hysterectomy (Hillis et al, 1998), which may include bilateral oophorectomy (Lowder et al, 2010), and thereby decrease breast cancer risk. Few studies have evaluated variation by tumours that expres