Life course breast cancer risk factors and adult breast density (United Kingdom)

Abstract

Objective: To determine whether risk factors in childhood and early adulthood affect later mammographic breast density. Methods: Subjects were 628 women who attended a medical examination at the University of Glasgow Student Health Service , responded to a questionnaire (2001) and had a screening mammogram in Scotland (1989Scotland ( -2002. Mammograms (median age of 59 years) were classified using a six category classification (SCC) of breast density percent. Logistic regression was used to determine associations between risk factors and having a high-risk mammogram ( 25% dense). Results: In multi-variable analyses, high-risk mammograms were associated with parity (adjusted odds ratio (OR) per child: 0.77 (95% confidence interval (CI) 0.61-0.99)), age at first birth, OR per year: 1.05 (0.99-1.11), smoking at university, OR smokers versus non-smokers: 0.58 (0.36-0.92) and body mass index (BMI) while at university, OR per 1 kg/m 2 0.75 (0.69-0.82). No associations with SCC were found for age at menarche, birth weight, oral contraceptive (OC) use, height, leg length or exercise at age 20. Conclusions: We confirm previous findings that breast density is affected by reproductive events and some anthropometric measures, however most of the risk factors acting throughout the life course which we examined were not closely related to adult breast density.

Measurements of Breast Density: No Ratio for a Ratio

“…Whereas our findings are quite similar to those reported by McCormack et al (18), Maskarinec et al (20) found an inverse relation. Other studies did not find any relation (15,16,19). This high variability in findings on the role of the age at menarche indicates that this early effect on breast density may be obscured or negated by other influences later in life and needs further investigation.…”

“…In these studies, factors including age, BMI, parity, passing through the menopause, and smoking have been shown to decrease the relative density. Factors including a late age at first birth, use of hormone therapy, and alcohol consumption have been found to increase the relative density (13)(14)(15)(16)(17)(18)(19)(20)(21).…”

“…Although the modern, continuous techniques determine the absolute amounts of total, dense, and nondense tissues on the mammogram, investigators usually still work with the ratio of dense over total tissue, or in other words, the relative amount of dense tissue (15)(16)(17)(18). The absolute amount of density was used in only a small number of studies, and of these, only the studies by Boyd et al and Heng et al made an inference about the difference in effects on absolute and relative densities (13,(19)(20)(21).…”

Early Life Factors and Incidence of Proliferative Benign Breast Disease

“…Many studies, including one in this population (23), have shown positive or J-shaped associations of birthweight with breast cancer risk (10). In addition, several recent studies have examined whether birthweight is associated with adult mammographic density, although their results are inconsistent (59)(60)(61). Greater birthweight may reflect higher concentrations of maternal estrogens during pregnancy (62,63) or may be an indicator of more rapid fetal growth (64).…”

Birth weight, childhood body mass index, and height in relation to mammographic density and breast cancer: a register-based cohort study

“…Although few studies have linked early-life factors to mammographic density (MD) [16-25], they are limited by small numbers of subjects and self-reported anthropometric data [16,18-20,22-25], and, as such, yield inconsistent results. Studies on birth weight and MD offer mixed evidence, showing none [16-18] or significant and positive associations [19-21].…”