Table 3.

Invasive breast cancer HRs and 95% CIs associated with years, intensity, and intensity-years of passive smoke exposure for 1,754 cases diagnosed 1997 to 2007 among 57,523 study participants

ExposurenNo. casesHR (95% CI)HR (95% CI)
Adjusted for age and raceAdjusted for age, race, and personal risk factors*
Years
    Lifetime exposures
        None7,0701631.001.00
        Low (≤15.0)16,5514361.12 (0.94-1.34)1.10 (0.92-1.32)
        Medium (15.1-30.0)16,3144951.13 (0.94-1.35)1.10 (0.92-1.32)
        High (>30.0)16,2996291.14 (0.96-1.36)1.12 (0.93-1.33)
    Age-specific exposures
        None7,0701631.001.00
        Age <20 exposure
            Low (≤15.0)14,7194411.13 (0.99-1.29)1.13 (0.99-1.29)
            Medium (15.1-30.0)19,1675910.99 (0.87-1.13)0.99 (0.87-1.13)
            High (>30.0)3,0171000.99 (0.79-1.24)0.98 (0.78-1.23)
        Age ≥20 exposure
            Low (≤15.0)22,9386331.06 (0.92-1.22)1.04 (0.90-1.20)
            Medium (15.1-30.0) 8,8883081.01 (0.86-1.20)1.00 (0.84-1.18)
            High (>30.0)8,9344091.19 (1.01-1.41)1.16 (0.98-1.38)
Intensity
    Lifetime exposures
        None7,0701631.001.00
        Low (≤2.0)25,5447781.11 (0.94-1.31)1.09 (0.92-1.29)
        Medium (2.1-3.0)9,3302921.11 (0.92-1.35)1.08 (0.89-1.31)
        High (>3.0)13,1934461.18 (0.98-1.41)1.14 (0.95-1.37)
    Age-specific exposures
        None7,0701631.001.00
        Age <20 exposure
            Low (≤2.0)26,2438201.07 (0.95-1.21)1.07 (0.95-1.21)
            Medium (2.1-3.0)4,8141310.94 (0.77-1.15)0.95 (0.77-1.16)
            High (>3.0)5,0151591.03 (0.84-1.26)1.04 (0.85-1.28)
        Age ≥20 exposure
            Low (≤2.0)22,7647141.04 (0.91-1.20)1.03 (0.89-1.18)
            Medium (2.1-3.0)7,4692441.08 (0.90-1.29)1.04 (0.87-1.24)
            High (>3.0)9,3413461.17 (0.98-1.39)1.13 (0.95-1.34)
Intensity-years
    Lifetime exposures
        None7,0701631.001.00
        Low (≤17.5)17,6184831.12 (0.94-1.34)1.10 (0.92-1.31)
        Medium (17.6-42.0)14,3564471.13 (0.94-1.35)1.10 (0.92-1.32)
        High (>42.0)15,8865801.14 (0.96-1.36)1.11 (0.93-1.32)
    Age-specific exposures
        None7,0701631.001.00
        Age <20 exposure
            Low (≤17.5)21,3756731.09 (0.96-1.23)1.09 (0.96-1.23)
            Medium (17.6-42.0)10,1562950.97 (0.83-1.13)0.97 (0.83-1.13)
            High (>42.0)4,1951270.99 (0.80-1.22)0.99 (0.80-1.22)
        Age ≥20 exposure
            Low (≤17.5)21,5146041.06 (0.92-1.22)1.04 (0.90-1.20)
            Medium (17.6-42.0)9,2133031.01 (0.85-1.19)0.99 (0.83-1.17)
            High (>42.0)8,5993891.22 (1.03-1.44)1.18 (1.00-1.40)
  • *Personal risk factors include family history of breast cancer, age at menarche, pregnancy history, lifetime duration of breast-feeding, physical activity, alcohol consumption, BMI, and categories of menopausal status with use of hormone therapy.

  • “Years” represents the sum of years of exposure across the three categories of home, work, and social.