A prospective study of the effects of early life growth on adult mammographic density

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It is now well-known that a woman's breast density, as measured by a breast scan, is a predictor of her future risk of breast cancer. It is also known that women who are heavier as babies and grow rapidly before age 7 are more likely to develop breast cancer in adult life. The effects were strongest in women who had early puberty. It has been suggested that there are critical points in early life growth that contribute to higher breast density in middle-age. Population-based surveys with early life growth data on large numbers of women that span birth to adulthood are necessary to estimate accurately the association between early life growth and breast density in middle age. Few such studies exist; Tasmanian Asthma Study is one of them. In 1968, all 4,194 female Tasmanian school children born in 1961 were surveyed and height and weight measured. Subsequently, weight and height measurements were carried out on samples of this cohort. We are currently conducting the 37-year follow-up of the TAS and to date have traced 87% and achieved a response rate of 77% (2,850) for a postal survey. This included self-reported weight and height measurements and detailed information reproductive history and the use of hormones. Weight, height and waist to hip ratio are currently measured on 600 of these respondents. We have access to school medical records of the full cohort, which have weight and height data measured at school medical inspections throughout school years, and maternal records so far for half of the total cohort, which have information on birth weight and length, and period of gestation. Hence, TAS now provides an ideal opportunity, unique within Australia, to investigate prospectively the association between early life growth and mammographic density in middle-age women. We will measure breast density in these women now they are in their late 40s, using the Australian Mammographic Density Research Facility at The University of Melbourne.