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. Author manuscript; available in PMC: 2009 Aug 1.
Published in final edited form as: Int J Cancer. 2008 Aug 1;123(3):664–671. doi: 10.1002/ijc.23564

TABLE IV.

RELATIVE RISKS (RR) OF CANCER AND LUNG CANCER ACCORDING TO CATEGORY OF CITRUS FRUIT/JUICE INTAKE 34,708 POSTMENOPAUSAL WOMEN IN THE IOWA WOMEN'S HEALTH STUDY STRATIFIED BY SMOKING HISTORY

Servings of citrus fruit or juice per week
 p for trend1
<4 4−8 >8
All cancer
    Never smokers
        Cases 1554 1225 1668
        Person-years 119,628 96,730 135,464
        Multivariate2 1.0 (reference) 0.96 (0.89−1.04) 0.93 (0.87−1.00) 0.06
    Ever smokers
        Cases 1322 780 892
        Person-years 70,458 43,019 54,512
        Multivariate2 1.0 (reference) 0.97 (0.89−1.07) 0.92 (0.84−1.01) 0.08
Lung Cancer
    Never smokers
        Cases 33 36 44
        Person-years 129,012 104,042 145,399
        Multivariate2 1.0 (reference) 1.26 (0.78−2.04) 1.12 (0.70−1.76) 0.61
    Ever smokers
        Cases 354 136 157
        Person-years 75,843 46,609 58,901
        Multivariate2 1.0 (reference) 0.75 (0.61−0.92) 0.73 (0.60−0.89) <0.01
1

Tests for trend across intake categories were performed by assigning each quintile its median intake value and treating the variable as a linear term.

2

Adjusted for age (years) and energy (kcal/day), education level (<high school, = high school, > high school), race (white/nonwhite), BMI (kg/m2), multivitamin use (yes/no), activity level (low, medium, high), and pack years (0, 1−19, 20−39, 40+).