Table 1.

Adjusted odds ratios for breast cancer associated with various smoking measures

VariableCases (n = 1,728)Controls (n = 441)Adjusted* odds ratio (95% confidence intervals)
Ever smoked 100 cigarettes?
    No9912611.00
    Yes7371800.99 (0.78-1.25)
    P, Wald χ20.93
Smoking status
    Never smoked9912611.00
    Former smoker4511121.04 (0.80-1.36)
    Current smoker286680.89 (0.64-1.24)
    P, Wald χ20.68
Total years of cigarette use
    Never smoked9912611.00
    ≤11 y238680.94 (0.68-1.30)
    >11 to ≤20 y216560.93 (0.66-1.31)
    >20 y283561.12 (0.79-1.59)
    Ptrend0.74
Age started smoking
    Never smoked9912611.00
    >18 y205550.94 (0.66-1.33)
    >15 to ≤18 y302611.20 (0.86-1.67)
    ≤15 y230640.83 (0.59-1.16)
    PTrend0.68
Lifetime cigarettes/wk
    Never smoked9912611.00
    ≤8 cigarettes/wk198580.87 (0.62-1.23)
    >8 to ≤52 cigarettes/wk270621.06 (0.76-1.47)
    >52 cigarettes/wk269601.03 (0.73-1.45)
    PTrend0.79
Cigarettes/wk in the last 5 y
    Never smoked9912611.00
    ≤14 cigarettes/wk101330.71 (0.46-1.11)
    >14 to ≤80 cigarettes/wk145320.95 (0.61-1.46)
    >80 cigarettes/wk152311.09 (0.70-1.70)
    Quit smoking >5 y ago339841.08 (0.80-1.44)
    PTrend0.78
Cigarettes/wk in a 5-y period after menarche
    Never smoked9912611.00
    ≤8 cigarettes/wk169341.15 (0.76-1.74)
    >8 to ≤28 cigarettes/wk126360.87 (0.57-1.33)
    >28 cigarettes/wk91300.82 (0.51-1.31)
    Did not smoke during this 5-y period351801.03 (0.76-1.39)
    PTrend0.45
Cigarettes/wk from age 10 to 18 y
    Never smoked9912611.00
    ≤5 cigarettes/wk176331.24 (0.81-1.88)
    >5 to ≤13 cigarettes/wk123400.72 (0.48-1.09)
    >13 cigarettes/wk138350.95 (0.62-1.44)
    Did not smoke before age 18 y300721.04 (0.76-1.42)
    PTrend§0.58
Smoked 1 y before age at first birth
    Never smoked6761941.00
    Did not smoke during year before first birth174570.92 (0.64-1.32)
    Smoked during year before first birth309651.27 (0.90-1.79)
    P, Wald χ20.28
Amount smoked 1 y before first birth
    Never smoked6761941.00
    Did not smoke 1 y before first birth174570.92 (0.64-1.31)
    ≤70 cigarettes/wk217421.35 (0.90-2.00)
    >70 cigarettes/wk92231.12 (0.67-1.89)
    P, Wald χ20.41
Years of smoking before first full-term pregnancy
    Never smoked9932611.00
    Smoked after first birth50120.97 (0.48-1.95)
    ≤10 y350920.95 (0.71-1.27)
    >10 y337761.03 (0.75-1.43)
    P, Wald χ20.98
  • * Adjusted for age, race, education, age at menarche, age at first full-term pregnancy, parity, average drinks per week in recent 5 y, and family history of breast or ovarian cancer.

  • Smokers who quit >5 y ago were excluded in the analysis for trend.

  • Smokers who did not smoke during the 5-y period after menarche were excluded in the analysis for trend.

  • § Smokers who did not smoke before age 18 y were excluded in the analysis for trend.

  • Nulliparous women were excluded from the analysis.