Table 1.

Risk factors for breast cancer among 126,638 women, NIH-AARP Diet and Health Study Cohort

No. cancersPerson-yearsRR* (95% CI)
Age at study entry (y)
    <57581128,537.41.00 (reference)
    57-60683129,840.91.30 (1.09-1.56)
    61-64839153,393.21.24 (0.99-1.56)
    65-681,031172,204.61.22 (0.94-1.59)
    ≥6952387,570.21.17 (0.87-1.57)
Race
    Caucasian3,372610,345.31.00 (reference)
    Other/unknown28561,201.00.87 (0.77-0.99)
Age at menarche (y)
    <131,833326,606.81.00 (reference)
    13-141,480278,978.20.92 (0.86-0.99)
    ≥1531360,337.30.91 (0.81-1.03)
Parity
    Nulliparous64597,513.31.00 (reference)
    138068,161.80.86 (0.75-0.97)
    2917173,999.80.79 (0.71-0.87)
    ≥31,643320,333.70.76 (0.70-0.84)
Age at first birth (y)
    Nulliparous64597,513.31.00 (reference)
    <20517110,683.20.74 (0.66-0.83)
    20-241,455291,956.70.74 (0.68-0.81)
    25-29710121,634.80.85 (0.76-0.94)
    ≥3027239,810.20.99 (0.86-1.15)
Menopausal status at baseline
    Premenopausal15525,326.41.18 (0.99-1.40)
    Natural menopause, <45 y21143,752.90.82 (0.71-0.95)
    Natural menopause, 45-49 y542103,254.70.90 (0.81-1.00)
    Natural menopause, 50-54 y1,088185,007.91.00 (reference)
    Natural menopause, ≥55 y31041,389.81.26 (1.11-1.43)
    Surgical menopause, <40 y460101,560.00.80 (0.72-0.89)
    Surgical menopause, 40-44 y32466,160.00.83 (0.73-0.94)
    Surgical menopause, 45-49 y28554,466.80.89 (0.78-1.01)
    Surgical menopause, ≥50 y17729,959.10.98 (0.84-1.15)
    Unknown type or menopausal age 285,716.00.79 (0.47-1.35)
BMI at baseline
    <251,579298,134.31.00 (reference)
    25-291,168210,824.91.07 (0.99-1.16)
    ≥30812144,254.71.13 (1.04-1.23)
No. breast biopsies
    None2,462506,112.41.00 (reference)
    1740105,286.01.41 (1.30-1.53)
    223029,313.41.56 (1.36-1.78)
    ≥319324,436.11.58 (1.36-1.83)
Family history of breast cancer
    No2,304460,680.61.00 (reference)
    Yes69889,974.41.48 (1.36-1.61)
No. mammograms
    ≤1968203,334.61.00 (reference)
    ≥22,668463,668.01.13 (1.05-1.22)
Alcoholic drinks per day
    Never954190,062.91.00 (reference)
    0-12,103390,924.61.05 (0.97-1.13)
    1-247672,081.81.25 (1.12-1.40)
    ≥312418,476.91.30 (1.08-1.57)
  • NOTE: Numbers of cancers and person-years shown are variable given that individuals with unknowns are not presented (31 cases for age at menarche, 72 for parity, 58 for age at first birth, 77 for menopausal status, 98 for BMI, 32 for breast biopsies, 655 for family history, and 21 for number of mammograms).

  • * RRs adjusted for age (continuous) and for race, age at first birth, menopausal status, number of breast biopsies, family history of breast cancer, and number of mammograms (per above categorizations).

  • Hysterectomy, bilateral oophorectomy, or both.