Table S2. Summary results of the studies on association between early life physical activity (5+ years before mammogram) and breast density

Author / Sample size / Results / Adjustments
Siozon, 2006 [76] / 375 / 10 Year time period before mammogram, premenopausal (adjusted mean percent density)
≤0.01 h/w: 32.2%
>0.01–1.9 h/w: 40.6%
≥2 h/w: 36.8%
P for trend 0.23 / 10 Year time period before mammogram, postmenopausal (adjusted mean percent density)
≤0.01 h/w: 22.2%
>0.01–1.9 h/w: 22.0%
≥2 h/w: 25.7%
P for trend 0.24 / Ethnicity, age at mammogram, age at menarche, parity, age at first full-term pregnancy, family history of breast cancer, OC use and menopausal and hormone use status. Additional adjustments: BMI, smoking, alcohol intake, and education.
Reeves, 2007 [77] / 728 / Data not shown. Results are reported to be the same at ages 18, 35, and 50 (see Table S1) / Age, BMI, race, age at first pregnancy >6 months, history of breast-feeding, number of breast biopsies, quality of film, interval between mammogram and questionnaire
Masala, 2009 [73] / 1,666 / Total physical activity
Inactive : OR=1.0
Moderately inactive: OR=1.17(95% CI 0.74-1.83)
Moderately active: OR=0.95 (95% CI 0.64-1.43)
Active: OR=0.96 (95% CI 0.57-1.60)
p for trend 0.46 / Occupational physical activity
Sedentary: OR=1.00
Standing: OR=1.10 (95% CI 0.75-1.62)
Manual/heavy manual: OR=1.00 (95% CI 0.60-1.68)
p for trend 0.93
No Paid Work: OR=1.13 / Age, education, weight, height, total caloric intake, each index separately, menopausal status
Gram, 1999 [31] / 2,720 / Work-time physical activity in 1979–1980 and 1986–1987
Sedentary (both times): OR=1.0 Some/mixture: OR=1.0 (95% CI 0.8–1.3)
Moderate (both times): OR=0.8 (95% CI 0.5–1.5) / Leisure-time physical activity in 1979–1980 and 1986–1987
Sedentary (both times): OR=1.0 Some/mixture: )R=1.1 (95% CI 0.8–1.6)
Moderate (both times): OR=0.9 (95% CI 0.5–1.7) / Age, education, menopausal status,
BMI, parity, age at menarche, OC use, and alcohol intake
Marmara, 2011 [21] / 724 / OR per one unit of MET =−0.10 (95% CI −0.018- −0.001), p=0.022 / Age at menarche (in years), age at menopause, BMI, and the number of live births

Abbreviations: BMI-Body Mass Index, kg/m²; OC-oral contraceptives; HRT-hormone replacement therapy; OR-odds ratio; 95% CI-95% Confidence interval; h/w-hours/week