Table S6. Summary results of the studies on association between physical activity and breast density in postmenopausal women

Author / Sample size / Results / Adjustments
Irwin, 2006 [60] / 323 / BMI<30(adjusted mean percent density)
less than ~ 2.5 h/week at a 3 MET level: 22.7%
~2.5–5 h/week at a 3 MET level: 21.5%
~5+ h/week at a 3 MET level: 21.5%
P for trend 0.60 / BMI≥30 (adjusted mean percent density)
less than ~ 2.5 h/week at a 3 MET level: 16.1
~2.5–5 h/week at a 3 MET level: 15.0%
~5+ h/week at a 3 MET level: 5.4%
Pfor trend 0.026 / Age, BMI, ethnicity, study site, education, parity, age at menarche, type 2 diabetes and current HRT use
Siozon, 2006 [76] / 227 / 10 Year time period prior to mammogram screening (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 / 3 Year time period prior to mammogram screening(adjusted mean percent density)
≤0.01 h/w: 22.0%
>0.01–1.9 h/w: 21.6%
≥2 h/w: 25.6%
P for trend 0.20 / Ethnicity, age at mammogram, age at menarche, parity, age at first full-term pregnancy, family history of breast cancer, oral contraceptive use and HRT use status; additional adjustments: BMI, smoking, alcohol intake, and education.
Samimi, 2008 [80] / 1029 / Women not currently on PMH PA (adjusted mean percent density)
< 3 METs/week: 24.0%
3-<9 METs/week: 22.2%
9-<15 METs/week: 19.4%
15-< 24 METs/week: 22.2%
≥24 METs/week: 20.9%
P for trend 0.16 / Women currently on PMH(adjusted mean percent density)
< 3 METs/week: 28.2%
3-<9 METs/week: 29.0%
9-< 5 METs/week: 30.5%
15-<24 METs/week: 27.1%
≥24 METs/week: 29.7%
P for trend 0.87 / BMI , parity/age at first birth, alcohol use, history of benign breast disease, family history of breast cancer and smoking status
Additionally adjusted for duration of PMH use and time since last PMH use
Masala, 2007 [73] / 1,056 / Total physical activity index
Inactive: OR=1.0
moderately inactive: OR=1.31 (95% CI 0.75-2.27)
moderately active: OR=0.99 (95% CI 0.61-1.62)
active: OR=0.98 (95% CI 0.53-1.81)
p for trend 0.43 / Age, education, weight, height, total caloric intake
Gram, 1999 [31] / 979 / Seldom/never : OR=1.0
≤2 h/week: OR=0.6 (95% CI 0.4–0.9)
>2 h/week: OR=0.8 (95% CI 0.4–1.3) / Age, education, menopausal status,
BMI, parity, age at menarche, OC use, and alcohol intake
Suijkerbuijk, 2006 [75] / 429 / Adjusted mean percent density
Inactive 33.4%
moderately inactive 35.2%
moderately active 33.3%
active 35.3% / BMI, waist-to-hip ratio, smoking, education, parity, and age
Vachon, 2000 [62] / 1520 / Adjusted mean percent density
Low physical activity index: 33%
Moderate: 31%
High: 31%
p for trend 0.25% / Age, age2, BMI, WHR, family history of breast cancer, education, alcohol, age at menarche, age at first birth and parity, smoking history, oral contraceptive use and HRT
Sellers, 2007 [29] / 1442 / Physical activity at age 7 (Adjusted mean percent density)
Less than average: 19.9%
Average: 19.2%
More than average: 18.1%
p for trend 0.8
Physical activity at age 12 (Adjusted mean percent density)
Less than average: 20.8%
Average: 19.7%
More than average: 19.2%
p for trend 0.3 / Physical activity at age 18 (Adjusted mean percent density)
Less than average: 20.2%
Average: 20.0%
More than average: 18.7%
p for trend 0.3 / Age at menarche, age at mammography, BMI at first follow-up, use of hormone replacement therapy, parity and age at first birth, OC use, alcohol consumption, education, adolescent and adult smoking status, and family history of breast cancer
Lopez, 2003 [19] / 294 / 1.5–3.0 vs. 0–1 hours of inactivity:β=0.38, (p=0.80)
3.5-20.0 vs. 0.1 hours of inactivity: β=3.26,(p=0.10) / Age, education, BMI, parity, menopausal status, HRT use, and smoking status

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; MET-metabolic equivalent