Weight at age 18 was inversely related to the risk of breast cancer. While women who lost more than 5 kg after age 18 were at a 23% reduced risk for breast cancer, those who gained more than 30 kg were at a 32% increased risk for breast cancer.
No risk for premenopausal breast cancer was seen for premenopausal weight gain, but a 37% increase in risk for postmenopausal breast cancer was reported for weight gain from age 18.
For the 2412 cases of ER+/PR+ breast cancer, among postmenopausal women there was a 50% increased risk for breast cancer with a weight gain of 30 kg after age 18. This direct association was not seen for ER+/PR- or ER-/PR- breast cancer.
“This is an important health concern,” Dr Rosner explained. “Weight is a modifiable risk factor and we found that in our cohort, attributable risk was 14% for postmenopausal breast cancer and 17% for ER+/PR+ breast cancer if women who gained more than 5 kg since age 18 did not change weight by more than 5 kg.”
Dr Rosner estimates that 14% of postmenopausal breast cancer could be prevented if women avoided excessive weight gain (more than 5 kg) after age 18.
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He acknowledged, however, that the study does not identify mechanism(s) associated with weight gain in premenopausal years and postmenopausal breast cancer. He also pointed out that of the women with breast cancer who die, 50% die from a cause other than breast cancer. “Our team will next look at the impact of weight gain on mortality,” he said.
- Rosner B, Eliassen AH, Toriola AT, et al. Weight and weight changes in early adulthood and later breast cancer risk. Int J Cancer. 2017 Jan 30. doi: 10.1002/ijc.30627 [Epub ahead of print]
- International Agency for Research on Cancer. Weight Control and Physical Activity, vol. 6. Lyon; 2002:315.
- Calle EE, Rodriguez C, Walker-Thurmond K, Thun MJ. Overweight, obesity, and mortality from cancer in a prospectively studied cohort of U.S. adults. N Engl J Med. 2003;348(17): 1625-38.
- Rosner BA, Colditz GA, Hankinson SE, Sullivan-Halley J, Lacey JV Jr, Bernstein L. Validation of Rosner-Colditz breast cancer incidence model using an independent data set, the California Teachers Study. Br Cancer Res Treat. 2013;142(1): 187-202.
- Rosner B, Colditz GA. Nurses’ health study: log-incidence mathematical model of breast cancer incidence. J Natl Cancer Inst. 1996;88(6): 359-64.
- Colditz GA, Rosner BA, Chen WY, Holmes MD, Hankinson SE. Risk factors for breast cancer according to estrogen and progesterone receptor status. J Natl Cancer Inst. 2004;96(3):218-28.