Department of Public Health, University of Copenhagen, Copenhagen, Denmark.
Nykøbing Falster Hospital, University of Copenhagen, Copenhagen, Denmark.
Int J Cancer. 2019 Dec 1;145(11):2954-2962. doi: 10.1002/ijc.32210. Epub 2019 Feb 27.
High mammographic density is a well-known risk factor for breast cancer. This study aimed to search for a possible birth cohort effect on mammographic density, which might contribute to explain the increasing breast cancer incidence. We separately analyzed left and right breast density of Dutch women from a 13-year period (2003-2016) in the breast cancer screening programme. First, we analyzed age-specific changes in average percent dense volume (PDV) across birth cohorts. A linear regression analysis (PDV vs. year of birth) indicated a small but statistically significant increase in women of: 1) age 50 and born from 1952 to 1966 (left, slope = 0.04, p = 0.003; right, slope = 0.09, p < 0.0001); 2) age 55 and born from 1948 to 1961 (right, slope = 0.04, p = 0.01); and 3) age 70 and born from 1933 to 1946 (right, slope = 0.05, p = 0.002). A decrease of total breast volume seemed to explain the increase in PDV. Second, we compared proportion of women with dense breast in women born in 1946-1953 and 1959-1966, and observed a statistical significant increase of proportion of highly dense breast in later born women, in the 51 to 55 age-groups for the left breast (around a 20% increase in each age-group), and in the 50 to 56 age-groups for the right breast (increase ranging from 27% to 48%). The study indicated a slight increase in mammography density across birth cohorts, most pronounced for women in their early 50s, and more marked for the right than for the left breast.
高乳房密度是乳腺癌的一个已知危险因素。本研究旨在寻找乳房密度可能存在的出生队列效应，这可能有助于解释乳腺癌发病率的上升。我们分别分析了荷兰女性在乳腺癌筛查项目中 13 年（2003-2016 年）的左、右乳房密度。首先，我们分析了各出生队列中平均致密体积百分比（PDV）的年龄特异性变化。PDV 与出生年份的线性回归分析表明，年龄为 50 岁且出生于 1952 年至 1966 年的女性（左乳斜率=0.04，p=0.003；右乳斜率=0.09，p<0.0001）；年龄为 55 岁且出生于 1948 年至 1961 年的女性（右乳斜率=0.04，p=0.01）；以及年龄为 70 岁且出生于 1933 年至 1946 年的女性（右乳斜率=0.05，p=0.002），PDV 略有增加。总乳房体积的减少似乎解释了 PDV 的增加。其次，我们比较了出生于 1946-1953 年和 1959-1966 年的女性中致密乳房的比例，发现较晚出生的女性中高度致密乳房的比例有统计学意义的增加，在左乳的 51 至 55 岁年龄组（每个年龄组增加约 20%），以及右乳的 50 至 56 岁年龄组（增加范围从 27%到 48%）。该研究表明，乳房密度在出生队列中略有增加，在 50 岁出头的女性中最为明显，右乳比左乳更为明显。
