Table 4.

Multivariate-adjusted RR of breast cancer in relation to updated smoking exposure variables stratified by vitamin A (retinol) and carotenoid tertiles (cumulative update of nutrients in 1991 and 1995)

Smoking variableVitamin A (retinol) tertiles (IU/day)
Total carotenoids tertiles (IU/day)
1 (<1749)2 (1749–3829)3 (>3829)1 (<6074)2 (6068–10,167)3 (>10,167)
Never smokers (reference)1.001.001.001.001.001.00
Years of smoking
    <100.911.511.381.391.610.87
    10–141.471.231.051.381.590.94
    15–191.240.581.431.231.160.92
    20+1.291.281.011.681.300.78
P for trend0.040.60.40.0030.070.2
P for interaction0.080.03
Never smokers (reference)1.001.001.001.001.001.00
No. cigarettes for current smokers
    1–40.391.170.891.611.350.62
    5–141.431.471.062.020.551.08
    15–241.680.770.981.621.330.61
    25+1.451.350.191.051.010.72
P for trend0.020.70.20.20.80.2
P for interaction0.40.08
Never smokers (reference)1.001.001.001.001.001.00
No. cigarettes for past smokers
    1–41.911.460.390.912.080.82
    5–141.381.341.321.721.430.94
    15–241.230.801.201.231.220.93
    25+1.290.831.471.461.591.03
P for trend0.20.50.20.10.11.0
P for interaction0.60.1
Never smokers (reference)1.001.001.001.001.001.00
Age at first smoking
    <151.351.351.591.501.960.94
    15–191.161.031.121.311.200.88
    20+1.411.170.961.561.320.86
P for interaction0.70.05
α-carotene tertiles (mg/day)β-carotene tertiles (mg/day)
1 (<432)2 (432–819)3 (>819)1 (<2902)2 (2902–4712)3 (>4712)
Never smokers (reference)1.001.001.001.001.001.00
Years of smoking
    <101.201.910.761.521.480.92
    10–141.261.540.931.441.411.03
    15–191.131.260.841.321.240.80
    20+1.501.270.811.771.100.87
P for trend0.020.070.20.0010.30.3
P for interaction0.050.06
Never smokers (reference)1.001.001.001.001.001.00
No. cigarettes for current smokers
    1–40.641.100.490.770.670.69
    5–141.561.600.742.130.771.23
    15–241.741.010.701.901.200.58
    25+0.940.981.251.230.721.22
P for trend0.21.00.90.070.80.9
P for interaction0.30.1
Never smokers (reference)1.001.001.001.001.001.00
No. cigarettes for past smokers
    1–41.141.850.821.401.980.63
    5–141.811.450.872.231.630.79
    15–240.891.260.981.120.821.14
    25+1.431.441.831.191.251.14
P for trend0.30.20.60.20.80.6
P for interaction0.10.001
Never smokers (reference)1.001.001.001.001.001.00
Age at first smoking
    <151.192.120.851.751.790.89
    15–191.301.140.871.341.19
    20+1.411.350.831.840.970.86
P for interaction0.020.03