Azam Shadi, Sjölander Arvid, Eriksson Mikael, Gabrielson Marike, Czene Kamila, Hall Per
JNCI Cancer Spectr. 2019 Feb 4;3(1):pkz004. doi: 10.1093/jncics/pkz004. eCollection 2019 Mar.
Mammographic density (MD) is a strong risk factor for breast cancer. We examined how breast cancer risk factors are associated with MD area (cm) change across age.
We conducted a cohort study of 31 782 Swedish women ages 40-70 years at time of baseline mammogram. Lifestyle and reproductive risk factors were assessed by a web-based questionnaire. MD was measured as dense area using the STRATUS method (mean over the left and right breast). Linear regression analyses with adjustments for age, body mass index (BMI), and menopausal status at baseline were performed to assess the association between breast cancer risk factors and mean baseline MD. To investigate mean MD change across age, linear regression analyses with adjustments for age, BMI, menopausal status, and age at last mammogram were performed. All tests of statistical significance were two-sided.
Except for oral contraceptive use, established lifestyle and reproductive risk factors for breast cancer were associated with baseline mean MD. The overall average annual MD change was -1.0 cm. BMI and physical activity were statistically significantly associated with MD change. Lean women (BMI <20 kg/m) had a mean MD change of -1.13 cm per year (95% confidence interval = -1.25 to -1.02) compared with -0.46 cm per year (95% confidence interval = -0.57 to -0.35) for women with BMI 30 or higher. The annual MD change was -0.4 cm larger in women who were very physically active compared with less physically active women.
Our results indicate that all risk factors for breast cancer, except oral contraceptive use, are associated with baseline MD but that only age, BMI, and physical activity are determinants of MD change.
乳腺钼靶密度（MD）是乳腺癌的一个重要风险因素。我们研究了乳腺癌风险因素如何随年龄变化与MD面积（平方厘米）相关。
我们对31782名年龄在40 - 70岁的瑞典女性进行了队列研究，这些女性在基线乳腺钼靶检查时参与研究。通过基于网络的问卷评估生活方式和生殖风险因素。使用STRATUS方法（左右乳房的平均值）将MD测量为致密面积。进行线性回归分析，对年龄、体重指数（BMI）和基线时的绝经状态进行调整，以评估乳腺癌风险因素与平均基线MD之间的关联。为了研究MD随年龄的变化情况，进行线性回归分析，并对年龄、BMI、绝经状态和最后一次乳腺钼靶检查时的年龄进行调整。所有统计学显著性检验均为双侧检验。
除口服避孕药的使用外，已确定的乳腺癌生活方式和生殖风险因素与基线平均MD相关。MD的总体平均年变化为 - 1.0平方厘米。BMI和身体活动与MD变化在统计学上显著相关。瘦女性（BMI <20 kg/m²）的MD平均每年变化为 - 1.13平方厘米（95%置信区间 = - 1.25至 - 1.02），而BMI为30或更高的女性为每年 - 0.46平方厘米（95%置信区间 = - 0.57至 - 0.35）。与身体活动较少的女性相比，身体活动非常活跃的女性每年的MD变化要大0.4平方厘米。
我们的结果表明，除口服避孕药的使用外，所有乳腺癌风险因素均与基线MD相关，但只有年龄、BMI和身体活动是MD变化的决定因素。
