Early life factors and adult mammographic density

Purpose Early life factors have shown to be related to breast cancer risk. The pathophysiological link could be mammographic density, a strong risk factor for breast cancer. Mammary gland development already starts in utero and early life factors might affect the number of mammary cells at risk. In this study, we investigated the association between early life factors and mammographic density in adulthood. Methods The study was conducted within 2,588, mainly postmenopausal women of the Prospect-European Prospective Investigation into Cancer and Nutrition cohort. This ongoing study recruited breast cancer screening participants who filled out extensive questionnaires. Information on the early life factors birth weight, gestational age, maternal and paternal age, multiple births, birth rank, exposure to parental smoking, and leg length as a proxy for growth at childhood was obtained using questionnaires. Generalized linear models and linear regression models were used to study the relation between early life factors and mammographic density. Analyses were adjusted for potential confounders. Results Women who had an older mother (p = 0.06) or father (p = 0.002) at birth tended to have a higher mammographic density. Furthermore, greater leg length seemed to be related to higher mammographic density, although not statistically significantly (p = 0.16). After adjustment for confounders, none of the early life factors showed any statistically significant relationship with mammographic density in adulthood. Conclusion Although we cannot exclude small effects that go undetected due to measurement error in recall of early life factors, the results suggest that mammographic density is not a major pathway in any observed relationship between these early life events and breast cancer risk