Influence of Lifestyle Factors on Mammographic Density in Postmenopausal Women

Judith S Brand,Fuat Celebioglu,Per Hall,Thang Trinh,Nirmala Bhoo-Pathy,Louise Eriksson,Kamila Czene,Sharon A Glynn

doi:10.1371/journal.pone.0081876

Abstract

BackgroundMammographic density is a strong risk factor for breast cancer. Apart from hormone replacement therapy (HRT), little is known about lifestyle factors that influence breast density.MethodsWe examined the effect of smoking, alcohol and physical activity on mammographic density in a population-based sample of postmenopausal women without breast cancer. Lifestyle factors were assessed by a questionnaire and percentage and area measures of mammographic density were measured using computer-assisted software. General linear models were used to assess the association between lifestyle factors and mammographic density and effect modification by body mass index (BMI) and HRT was studied.ResultsOverall, alcohol intake was positively associated with percent mammographic density (P trend = 0.07). This association was modified by HRT use (P interaction = 0.06): increasing alcohol intake was associated with increasing percent density in current HRT users (P trend = 0.01) but not in non-current users (P trend = 0.82). A similar interaction between alcohol and HRT was found for the absolute dense area, with a positive association being present in current HRT users only (P interaction = 0.04). No differences in mammographic density were observed across categories of smoking and physical activity, neither overall nor in stratified analyses by BMI and HRT use.ConclusionsIncreasing alcohol intake is associated with an increase in mammography density, whereas smoking and physical activity do not seem to influence density. The observed interaction between alcohol and HRT may pose an opportunity for HRT users to lower their mammographic density and breast cancer risk.

Highlights

Percent mammographic density refers to the relative amount of fibroglandular to fat tissue in the breast and is a major risk factor for breast cancer with risk being 4–6 fold higher in women with extremely dense breasts (.75%) compared to women having fatty or non-dense breasts (,5%) [1]
A large number of studies have examined the effect of lifestyle factors on mammographic density in postmenopausal women, but except for hormone replacement therapy (HRT) results have not been entirely consistent
We examined associations between alcohol, smoking and physical activity with different mammographic measures while taking potential interactions with body mass index (BMI) and HRT use into account

Summary

Introduction

Percent mammographic density refers to the relative amount of fibroglandular to fat tissue in the breast and is a major risk factor for breast cancer with risk being 4–6 fold higher in women with extremely dense breasts (.75%) compared to women having fatty or non-dense breasts (,5%) [1]. Because of its strong association with breast cancer, it is plausible that factors influencing mammographic density may contribute to breast cancer risk. Identification of such factors will improve our understanding of breast cancer etiology, but may provide an avenue for cancer prevention in the instances when the risk factors are modifiable. A large number of studies have examined the effect of lifestyle factors on mammographic density in postmenopausal women, but except for hormone replacement therapy (HRT) results have not been entirely consistent. An inverse association has been reported [13,14,15], but in the majority of studies no difference in mammographic density with physical activity levels was found [16]

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Results

Conclusion