Table 2.

ORs and 95% CIs for breast cancer incidence according to quartile of plasma ferritin (ng/mL) in the NHSII

Plasma ferritin quartile, ng/mL
≤23.9>23.9–≤42.1>42.1–≤72.0>72.0P valuea
Overall
 Cases/controls196/198217/199177/199205/199
 Simpleb1.00 (ref)1.11 (0.84–1.46)0.89 (0.67–1.19)1.04 (0.77–1.40)0.99
 Multivariatec1.00 (ref)1.04 (0.78–1.39)0.85 (0.62–1.15)1.05 (0.77–1.45)0.77
Invasive
 Cases/controls127/198155/199126/199142/199
 Multivariated1.00 (ref)1.21 (0.88–1.66)0.96 (0.69–1.33)1.06 (0.75–1.49)0.90
ER+/PR+
 Cases/controls82/198105/19988/19995/199
 Multivariated1.00 (ref)1.31 (0.91–1.89)1.08 (0.74–1.59)1.14 (0.77–1.69)0.88
ER/PR
 Cases/controls26/19826/19915/19919/199
 Multivariated1.00 (ref)0.93 (0.51–1.70)0.54 (0.27–1.08)0.70 (0.35–1.39)0.24
Premenopausal at diagnosis
 Cases/controls113/117127/12188/10078/64
 Multivariated1.00 (ref)1.02 (0.70–1.48)0.87 (0.58–1.30)1.21 (0.77–1.88)0.47
Postmenopausal at diagnosis
 Cases/controls62/6662/5171/73104/111
 Multivariated1.00 (ref)1.37 (0.79–2.37)1.11 (0.65–1.88)1.09 (0.65–1.83)0.87
  • aP values from tests for trend.

  • bConditional logistic regression model accounting only for matching factors.

  • cConditional logistic regression model accounting for matching factors and further adjusted for age at menarche (<12, 12, 13, and ≥14 years), BMI at age 18 (<18.5, 18.5–<21, 21–<23, and ≥23 kg/m2), weight change since age 18 (<5, 5–<20, and ≥20 kg), parity and age at first birth (nulliparous, 1–2 children and <25 years, 1–2 children and 25–29 years, 1–2 children and ≥30 years, ≥3 children and <25 years, ≥3 children and ≥25 years), family history of breast cancer (yes, no), personal history of benign breast disease (yes, no).

  • dUnconditional logistic regression model adjusted for covariates in the other multivariate models and adjusted for matching factors: age at blood draw (continuous), race (Caucasian, other), menopausal status at blood draw (premenopausal, postmenopausal, unknown menopausal status), menopausal status at diagnosis (premenopausal, postmenopausal, unknown menopausal status), month of blood draw (continuous), luteal day at blood draw (<8, ≥8, untimed collected), time of day at blood draw (12 am–8 am, 9 am–12 pm, and 1 pm–11 pm), fasting status at blood draw (yes, no).