Weight change and risk of postmenopausal breast cancer (United States)

Objective: Although many studies have shown that higher weight increases th e risk of postmenopausal breast cancer, some aspects of this association ar e unclear. In order to examine the risk associated with different patterns of weight change, we analyzed data from a large case-control study of postm enopausal breast cancer. Methods: Participants included women aged 50-79 years (n = 5031) who are ne wly diagnosed with invasive breast cancer in Massachusetts, New Hampshire, and Wisconsin. Similarly-aged population controls (n = 5255) were selected at random from driver's license files and Medicare beneficiary lists. Heigh t, weight, and information on other breast cancer risk factors were ascerta ined by structured telephone interviews from 1992 to 1995, and logistic reg ression was used to estimate multivariable-adjusted odds ratios (OR) and 95 % confidence intervals (CI). Results: Women in the top quintile groups for height at age 20, recent weig ht, and recent body mass index had significantly increased risks of breast cancer. Among women who reached their highest adult weight at younger ages (less than or equal to 45 years), increasing weight loss since that age was associated with a reduced risk of postmenopausal breast cancer (OR 0.90, C I 0.84-0.98, per 5 kg). However, weight loss among women whose highest weig ht occurred after age 45 was not associated with risk (OR 1.00, CI 0.95-1.0 5, per 5 kg). Weight gain since the lowest adult weight increased risk by 8 % for each 5 kg of gain (OR 1.08, CI 1.06-1.11). Temporary weight cycling ( weight loss followed by weight gain) was not associated with increased risk . Conclusions: Weight gain clearly increased risk of postmenopausal breast ca ncer. These data lend further support to efforts aimed at helping women avo id weight gain as they age.