Bottom Line: Higher body mass index (BMI), especially in early adulthood, may be associated with reduced risk for premenopausal breast cancer.
Why The Research Is Interesting: Breast cancer is the most commonly diagnosed cancer among women. Breast cancer’s origin is complex and it includes a wide range of factors, among them how much body fat a woman has, a measure often assessed by BMI (a calculation of weight in kilograms divided by height in meters squared). Previous research suggests increasing BMI may be associated with reduced risk for premenopausal breast cancer but increased risk after menopause. This study sought to undertake a more rigorous and systematic analysis of the association between BMI and risk of premenopausal breast cancer using pooled data from 19 studies.
Who and When: 758,592 premenopausal women from 19 studies (recruited from 1963 to 2013); there were 13,082 new cases of breast cancer over roughly nine years of follow-up per participant
What (Study Measures and Outcomes): BMI at ages 18 to 24, 25 to 34, 35 to 44 and 45 to 54 (exposures); invasive or noninvasive (in situ) premenopausal breast cancer
Study Design: This was an observational study. Researchers were not intervening for purposes of the study
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