Table 1.

Associations between participant characteristics and breast cancer risk among female VITAL participants (n = 35,016)

CharacteristicCases (n = 880), n (%)Noncases (n = 34,136), n (%)Age-adjusted HR (95% CI)
Demographics
    Age at baseline (y)
        <55101 (11.5)7,224 (21.2)N/A
        55 to <60190 (21.6)8,333 (24.4)
        60 to <65181 (20.6)6,346 (18.6)
        65 to <70183 (20.8)5,492 (16.1)
        ≥70225 (25.6)6,741 (19.8)
    Race
        White828 (95.3)31,103 (93.1)1.00 (reference)
        Non-white41 (4.7)2,297 (6.9)0.69 (0.51-0.95)
    Education
        ≤High school graduate223 (25.7)8,149 (24.4)1.00 (reference)
        Some college348 (40.1)13,923 (41.7)1.01 (0.86-1.20)
        College or advanced degree297 (34.2)11,294 (33.9)1.12 (0.94-1.33)
        P trend0.21
Anthropometrics
    BMI (kg/m2)
        <25313 (37.4)13,061 (41.0)1.00 (reference)
        25 to <30301 (36.0)10,668 (33.5)1.16 (0.99-1.36)
        ≥30222 (26.6)8,116 (25.5)1.20 (1.01-1.42)
        P trend0.03
    Height (cm)
        <15866 (7.6)3,043 (9.1)1.00 (reference)
        158 to <165297 (34.1)13,179 (39.5)1.02 (0.78-1.34)
        165 to <173379 (43.5)12,732 (38.2)1.37 (1.05-1.77)
        ≥173130 (14.9)4,375 (13.1)1.40 (1.04-1.88)
        P trend<0.0001
Lifestyle
    Fruit consumption (servings/day)
        0-1.04272 (34.5)10,115 (33.2)1.00 (reference)
        1.05-2.14271 (34.4)10,171 (33.4)0.95 (0.81-1.13)
        >2.14246 (31.2)10,186 (33.4)0.86 (0.73-1.02)
        P trend0.09
    Vegetable consumption (servings/day)
        0-1.73270 (34.2)10,173 (33.4)1.00 (reference)
        1.73-2.85251 (31.8)10,119 (33.2)0.92 (0.77-1.09)
        >2.85268 (34.0)10,180 (33.4)0.97 (0.82-1.15)
        P trend0.74
    Alcohol (g/d)
        0 to <0.5367 (42.4)15,072 (45.6)1.00 (reference)
        0.5 to <1.589 (10.3)4,259 (12.9)0.89 (0.71-1.13)
        1.5 to <5115 (13.3)4,860 (14.7)1.01 (0.82-1.24)
        5 to <1095 (11.0)3,495 (10.6)1.15 (0.92-1.44)
        ≥10199 (23.0)5,360 (16.2)1.54 (1.30-1.83)
        P trend<0.0001
    10-y physical activity (MET hours/week)
        0138 (15.8)5,112 (15.2)1.00 (reference)
        Tertile 1: 0 to <3.33262 (30.1)9,539 (28.3)1.01 (0.82-1.24)
        Tertile 2: 3.33-10.62234 (26.9)9,481 (28.2)0.90 (0.73-1.11)
        Tertile 3: >10.62237 (27.2)9,536 (28.3)0.90 (0.73-1.11)
        P trend0.15
Reproductive history
    Age at menarche (y)*
        ≤11181 (20.6)6,279 (18.5)1.00 (reference)
        12671 (30.9)10,123 (29.8)0.93 (0.77-1.12)
        13242 (27.7)9,987 (29.4)0.83 (0.68-1.00)
        ≥14183 (20.8)7,593 (22.3)0.80 (0.65-0.98)
        P trend0.01
    Age at first birth (y)
        ≤19134 (15.3)6,227 (18.4)1.00 (reference)
        20-24379 (43.4)14,095 (41.5)1.20 (0.98-1.46)
        25-34205 (23.5)8,707 (25.7)1.15 (0.92-1.43)
        ≥3525 (2.9)677 (2.0)1.95 (1.27-3.00)
        Nulligravid131 (15.0)4,229 (12.5)1.64 (1.29-2.09)
        P trend<0.0001
    Hysterectomy
        None564 (64.1)20,332 (59.6)1.00 (reference)
        Simple168 (19.1)7,615 (22.3)0.73 (0.62-0.87)
        Total or bilateral oopherectomy148 (16.8)6,189 (18.1)0.83 (0.69-0.99)
    Combined hormone therapy (y)
        Never462 (56.0)20,281 (63.0)1.00 (reference)
        1-491 (11.0)4,432 (13.8)1.04 (0.82-1.30)
        5-9110 (13.3)3,592 (11.2)1.40 (1.14-1.73)
        ≥10162 (19.6)3,898 (12.1)1.68 (1.40-2.01)
        P trend<0.0001
Medical history
    Number of first-degree relatives with breast cancer
        None675 (78.7)28,532 (84.7)1.00 (reference)
        1162 (18.9)4,616 (13.7)1.46 (1.23-1.73)
        ≥221 (2.5)475 (1.4)1.75 (1.13-2.70)
        P trend<0.0001
    Had benign breast biopsy
        No652 (74.1)27,916 (81.8)1.00 (reference)
        Yes228 (25.9)6,220 (18.2)1.50 (1.29-1.75)
    NSAID use
        Irregular672 (77.5)25,975 (77.0)1.00 (reference)
        Regular195 (22.5)7,765 (23.0)0.91 (0.78-1.07)
  • *Among women who have had a period.

  • Ten-year average use: irregular, <4 d/week or <4 y; regular, ≥4 d/week and ≥4 y.