Changes in weight and waist circumference during menopausal transition and postmenopausal breast cancer risk.

Our study aimed to investigate the association between changes in weight and waist circumference (WC) during menopausal transition and breast cancer risk in Asian women. In total, 184 931 women aged 40 to 59 years with a premenopausal status at the first screening in 2009 to 2010 and a postmenopausal status at the second screening in 2011 to 2012 were included in the analysis. Changes in weight and WC during menopausal transition were classified as loss (>2.5 kg; >2.5 cm), stable (±2.5 kg; ±2.5 cm), and gain (2.5-4.9 kg, ≥5 kg; 2.5-4.9 cm, ≥5 cm). WC gain of 5 cm or more during menopausal transition was associated with an increased risk of breast cancer with an HR of 1.15 (95% CI = 1.01-1.30), compared to stable WC (±2.5 cm). Among obese premenopausal women, increased WC ≥5 cm during menopausal transition was associated with increased breast cancer risk with an HR of 1.22 (95% CI = 1.03-1.44). Similarly, in women with premenopausal WC ≥80 cm, increased WC of ≥5 cm during menopausal transition was likely to increase the breast cancer risk (HR = 1.36, 95% CI = 1.13-1.88) than in women with stable WC. However, in premenopausal women with BMI <23 kg/m2 or WC <80 cm, changes in WC during menopausal transition did not show an association. Weight gain during menopausal transition was not associated with the risk of breast cancer. Changes in central obesity during menopausal transition in combination with premenopausal obesity status are associated with breast cancer risk after menopause.