Table 5

OR estimates of breast cancer by time of first occurrence of infectious mononucleosis and tonsillectomy

ConditionTime of first occurrence (no. of cases/controls)Age-adjustedMultivariable-adjusteda
OR estimate95% CIOR estimate95% CI
IMNever had (503/469)1.00(Reference)1.00(Reference)
Ages 0–9 (1/2)0.55b0.05–6.170.41c0.03–5.09
Ages 10–19 (7/9)0.74b0.27–2.040.70c0.25–1.97
Ages 20–24 (9/6)1.58b0.55–4.541.29c0.44–3.79
Ages ≥25 (17/6)2.67b1.04–6.892.41c0.92–6.32
TonsillectomyNever had (175/178)1.00(Reference)1.00(Reference)
Ages 0–4 (41/45)0.92d0.57–1.480.82e0.50–1.35
Ages 5–9 (170/159)1.08d0.79–1.461.05e0.76–1.43
Ages 10–14 (71/64)1.13d0.76–1.691.08e0.72–1.64
Ages ≥15 (80/46)1.76d1.15–2.691.68e1.09–2.60
IMNever had (503/469)1.00(Reference)1.00(Reference)
Before menarche (2/2)1.100.15–7.920.800.10–6.28
After menarche (32/21)1.450.82–2.581.300.72–2.34
Never had (503/469)1.00(Reference)1.00(Reference)
Before FFTPf (19/14)1.350.67–2.761.120.54–2.33
After FFTPf (12/7)1.670.65–4.331.570.60–4.15
Nulliparous (3/2)1.190.19–7.571.130.17–7.50
TonsillectomyNever had (175/178)1.00(Reference)1.00(Reference)
Before menarche (270/254)1.070.82–1.411.030.78–1.37
After menarche (92/60)1.541.04–2.281.470.98–2.20
Never had (175/178)1.00(Reference)1.00(Reference)
Before FFTPf (299/274)1.100.84–1.441.090.80–1.45
After FFTPf (18/10)1.800.80–4.031.960.85–4.50
Nulliparous (45/30)1.540.92–2.581.130.50–2.59
  • a Adjusted for age, family history of breast cancer, number of full-term pregnancy, age at first full-term pregnancy, body mass index, age at menarche, use of hormone replacement therapy, cumulative duration of oral contraceptive use, and alcohol consumption.

  • b P for trend = 0.016.

  • c P for trend = 0.043.

  • d P for trend = 0.018.

  • e P for trend = 0.042.

  • f FFTP, first full-term pregnancy.