American Journal of Epidemiology © The Author(s) 2018. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: email@example.com. Letter to the Editor RE: “GROWTH TRAJECTORIES, BREAST SIZE, AND BREAST-TISSUE COMPOSITION IN A BRITISH PREBIRTH COHORT OF YOUNG WOMEN” We read with great interest the important paper by Denholm between size and growth at different time points and breast tissue et al. (1) examining growth trajectories from birth through ado- composition. For example, was the inverse association between lescence and their association with breast tissue composition percentage of fat mass in adolescence the same for girls who (volume and density), as assessed by magnetic resonance imag- were born big with stable postnatal growth and girls who were ing(MRI), in womenaged21years. Their ﬁndings of a positive smaller at birth and experienced catch-up growth in infancy or association of breast density (as measured by MRI percent water) early childhood? Further examination of these growth patterns with birth weight and an inverse association of breast density and breast tissue composition may provide additional insight with pubertal weight growth, weight velocity from ages 10 to 21 into why the positive association between birth weight and years, and percentage of body fat from ages 9 to 13.5 years are breast cancer risk (7) reverses direction by adolescence, when consistent with the evidence based on adolescent body size and body mass index has a consistent inverse relationship with mammographic breast density (MBD) and breast cancer risk (2). breast cancer risk (2). What makes their cohort unique, however, is that they also have measures of early-life growth, including growth in infancy. There are few data on infant growth and MBD, but we recently ACKNOWLEDGMENTS conducted a study examining infant growth and MBD and found Conﬂict of interest: none declared. inverse associations between infant weight gain and MBD (3). Infancy is a dynamic period when most babies triple their birth weight in just 12 months. Infancy is also a time that has been associated with “minipuberty,” when endogenous steroid and REFERENCES growth hormones rapidly change, stimulating breast tissue 1. Denholm R, De Stavola B, Hipwell JH, et al. Growth trajectories, growth which later regresses in most girls (4). We believe that breast size, and breast-tissue composition in a British prebirth cohort focused investigation of the infant period might help explain of young women. Am J Epidemiol. 2018;187(6):1259–1268. the reversal of association between the positive relationship of 2. Terry MB. Consistency, now what? [editorial]. Breast Cancer breast cancer risk with birth weight and the inverse relation- Res. 2017;19:85. ship of breast cancer risk with larger body size in later child- 3. Akinyemiju TF, Tehranifar P, Flom JD, et al. Early life hood and adolescence. growth, socioeconomic status, and mammographic breast Denholm et al. reported that they did not ﬁnd an association density in an urban US birth cohort. Ann Epidemiol. 2016; between rate of height or weight growth in infancy and early 26(8):540–545.e2. childhood (assessed by changes in z scores from birth to age 4. Kuiri-Hänninen T, Sankilampi U, Dunkel L. Activation of the hypothalamic-pituitary-gonadal axis in infancy: minipuberty. 3 months, age 3 months to age 12 months, age 1 year to age Horm Res Paediatr. 2014;82(2):73–80. 3 years, and age 3 years to age 7 years) and total breast volume 5. Tu YK, Tilling K, Sterne JA, et al. A critical evaluation of or MRI percent water (1). However, these results came from statistical approaches to examining the role of growth models that included birth size and growth measurements taken trajectories in the developmental origins of health and disease. in all time periods from birth to age 21 years. The estimate Int J Epidemiol. 2013;42(5):1327–1339. for weight gain earlier in life becomes difﬁcult to interpret 6. Baird J, Fisher D, Lucas P, et al. Being big or growing fast: when conditioned on later growth (5). Interpretation of the systematic review of size and growth in infancy and later coefﬁcient for the relationship between weight gain from obesity. BMJ. 2005;331(7522):929. birth to age 3 months and MRI percent water, for example, 7. Michels KB, Xue F. Role of birthweight in the etiology of breast in these fully adjusted models is the direct effect of early cancer. Int J Cancer 2006;119(9):2007–2025. infant weight gain that is independent of later growth. Since 1 1,2 infant weight gain is associated with later childhood body size Mandy Goldberg and Mary Beth Terry (6), there is also an indirect effect of infant weight gain on later (e-mail: firstname.lastname@example.org) breast density through later measures of childhood and adoles- Department of Epidemiology, Mailman School of Public cent growth. We believe it would be of great interest to also Health, Columbia University, New York, NY consider the total effect of infant weight gain on breast tissue Herbert Irving Comprehensive Cancer Center, Columbia composition, which includes both direct and indirect effects, University, New York, NY without adjusting for subsequent growth. The detailed, repeated growth data collected in this important DOI: 10.1093/aje/kwy107 cohort would also allow for the consideration of interactions Downloaded from https://academic.oup.com/aje/advance-article-abstract/doi/10.1093/aje/kwy107/5001691 by Ed 'DeepDyve' Gillespie user on 12 July 2018
American Journal of Epidemiology – Oxford University Press
Published: May 23, 2018
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