Table 3 Estimates obtained from a linear-mixed regression model with 95% confidence intervals (CI) showing the change in absolute (cm³) and percent (%) dense volume in each breast over three consecutive screening rounds and association with breast cancer for 42,894 women screened in BreastScreen Norway, 2007–2020

Age at first screening examination (years)

-0.006 (-0.008; -0.005)

< 0.001

-0.007 (-0.008; -0.005)

< 0.001

Breast volume (cm³)

0.0002 (0.0002; 0.0002)

< 0.001

-0.0004 (-0.0004; -0.0004)

< 0.001

Benign breast disease (ever in BreastScreen Norway)

0.003 (-0.010; 0.016)

0.61

0.009 (-0.003; 0.021)

0.14

Follow-up time (screening round)

-0.010 (-0.010; -0.009)

< 0.001

-0.013 (-0.014; -0.013)

< 0.001

Breast not developing cancer

0.060 (0.042; 0.079)

< 0.001

0.063 (0.046; 0.080)

< 0.001

Breast developing cancer

0.056 (0.038; 0.075)

< 0.001

0.058 (0.040; 0.075)

< 0.001

Breasts without cancer^&

Reference

Reference

Follow-up time*breast not developing cancer

0.002 (-0.003; 0.007)

0.42

0.003 (-0.002; 0.007)

0.30

Follow-up time*breast developing cancer

0.009 (0.004; 0.014)

< 0.001

0.009 (0.004; 0.014)

< 0.001

Body mass index (kg/m²)

-0.0004 (-0.0009; 0.00007)

0.09

-0.005 (-0.005; -0.004)

< 0.001

First- or second-degree family history (versus no)

0.010 (0.004; 0.017)

0.003

0.001 (0.004; 0.016)

0.002

Use of hormone therapy after menopause (ever versus never)

0.002 (-0.002; 0.006)

0.35

-0.001 (-0.005; 0.003)

0.52

Use of alcohol (ever versus never)

0.023 (0.018; 0.028)

< 0.001

0.015 (0.010; 0.019)

< 0.001

Smoking (ever versus never)

-0.007 (-0.011; -0.003)

0.001

-0.010 (-0.014; -0.006)

< 0.001

Constant

2.90 (2.82; 2.97)

< 0.001

2.02 (1.95; 2.08)

< 0.001

Random effect constant variance

0.042 (0.041; 0.042)

n.a.

0.034 (0.034; 0.035)

n.a