Research article

Body fatness during childhood and adolescence and incidence of breast cancer in premenopausal women: a prospective cohort study

Heather J Baer^1,2 , Graham A Colditz^1,2,3 , Bernard Rosner^1,4 , Karin B Michels^1,2,5 , Janet W Rich-Edwards^1,2,6 , David J Hunter^1,2,7 and Walter C Willett^1,2,7

¹  Channing Laboratory, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts, USA

²  Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts, USA

³  Harvard Center for Cancer Prevention, Boston, Massachusetts, USA

⁴  Department of Biostatistics, Harvard School of Public Health, Boston, Massachusetts, USA

⁵  Obstetrics and Gynecology Epidemiology Center, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA

⁶  Department of Ambulatory Care and Prevention, Harvard Pilgrim Health Care and Harvard Medical School, Boston, Massachusetts, USA

⁷  Department of Nutrition, Harvard School of Public Health, Boston, Massachusetts, USA

author email corresponding author email

Breast Cancer Research 2005, 7:R314-R325doi:10.1186/bcr998

Published:	18 February 2005

see related Commentary: http://breast-cancer-research.com/content/7/3/83

Abstract

Introduction

Body mass index (BMI) during adulthood is inversely related to the incidence of premenopausal breast cancer, but the role of body fatness earlier in life is less clear. We examined prospectively the relation between body fatness during childhood and adolescence and the incidence of breast cancer in premenopausal women.

Methods

Participants were 109,267 premenopausal women in the Nurses' Health Study II who recalled their body fatness at ages 5, 10 and 20 years using a validated 9-level figure drawing. Over 12 years of follow up, 1318 incident cases of breast cancer were identified. Cox proportional hazards regression was used to compute relative risks (RRs) and 95% confidence intervals (CIs) for body fatness at each age and for average childhood (ages 5–10 years) and adolescent (ages 10–20 years) fatness.

Results

Body fatness at each age was inversely associated with premenopausal breast cancer incidence; the multivariate RRs were 0.48 (95% CI 0.35–0.55) and 0.57 (95% CI 0.39–0.83) for the most overweight compared with the most lean in childhood and adolescence, respectively (P for trend < 0.0001). The association for childhood body fatness was only slightly attenuated after adjustment for later BMI, with a multivariate RR of 0.52 (95% CI 0.38–0.71) for the most overweight compared with the most lean (P for trend = 0.001). Adjustment for menstrual cycle characteristics had little impact on the association.

Conclusion

Greater body fatness during childhood and adolescence is associated with reduced incidence of premenopausal breast cancer, independent of adult BMI and menstrual cycle characteristics.