Table 2

Age-adjusted ORs and 95% CIs for HER-2/neu-positive (+) and HER-2/neu-negative (−) breast cancer in relation to known and suspected risk factors among women <45 years of age in New Jersey, 1990–1992

Controls (n = 462)HER-2/neu+ cases (n = 159)HER-2/neu− cases (n = 212)Age-adjusted OR (95% CI)Ratio of the ORs (95% CI)
HER-2/neu+HER-2/neu
Oral contraceptives
 OC use
  Never16848761.01.0
  Ever2941111361.33 (0.90–1.96)1.03 (0.73–1.44)1.29 (0.83–2.00)
 OC duration (years)a
  <53718181.30 (0.85–2.00)1.00 (0.69–1.47)1.30 (0.80–2.11)
  5–98127371.19 (0.69–2.05)1.03 (0.64–1.66)1.16 (0.63–2.14)
  ≥1017666811.75 (0.91–3.36)1.13 (0.60–2.13)1.55 (0.73–3.27)
 Age at first use of OCs (in years)a
  <184020131.91 (1.01–3.59)0.80 (0.40–1.59) 2.39 (1.08–5.30)
  18–2115248811.10 (0.70–1.74)1.18 (0.80–1.73)0.94 (0.56–1.56)
  ≥2210243421.45 (0.90–2.35)0.89 (0.56–1.39)1.64 (0.94–2.87)
 Number of years since first usea
  <158629321.37 (0.77–2.44)0.96 (0.56–1.63)1.43 (0.73–2.81)
  15–1911339411.21 (0.74–1.97)0.83 (0.53–1.32)1.45 (0.81–2.57)
  ≥209543631.44 (0.86–2.41)1.28 (0.81–2.00)1.13 (0.64–1.98)
 Number of years since last usea
  <14313191.25 (0.60–2.59)1.29 (0.68–2.45)0.97 (0.42–2.22)
  1–43615131.66 (0.68–2.45)0.99 (0.49–2.01)1.67 (0.72–3.90)
  5–94115251.37 (0.70–2.70)1.50 (0.84–2.66)0.92 (0.44–1.92)
  ≥1017468791.27 (0.82–1.96)0.89 (0.60–1.31)1.42 (0.87–2.34)
Reproductive factors
 Parous
  Ever3611251641.01.0
  Never10134481.06 (0.67–1.66)1.21 (0.81–1.82)0.87 (0.52–1.46)
 Age at first birth (each additional year)1.02 (0.98–1.06)1.05 (1.02–1.09)0.96 (0.92–1.01)
 Children (number, among parous only)
  19228431.01.0
  216159821.18 (0.71–2.00)1.05 (0.67–1.65)1.03 (0.63–2.02)
  ≥310838391.13 (0.64–2.00)0.73 (0.43–1.23)1.55 (0.80–2.99)
 Lactation (among parous women)
  Never17968771.01.0
  Ever17757860.92 (0.61–1.40)1.29 (0.88–1.88)0.72 (0.44–1.15)
 Age at menarche (years)
  8–12230881211.01.0
  ≥1323271910.80 (0.56–1.16)0.73 (0.52–1.10)1.10 (0.72–1.67)
Other factors
 Family history of breast cancer
  None4311361791.01.0
  First degree3123332.27 (1.28–4.03)2.44 (1.44–4.12)0.93 (0.52–1.67)
 Previous biopsy
  None4401451871.01.0
  ≥12214251.89 (0.94–3.80)2.52 (1.38–4.60)0.75 (0.37–1.50)
 Body size (body mass index)
  <2317164871.01.0
  23–2614949580.82 (0.53–1.29)0.68 (0.45–1.02)1.21 (0.73–2.01)
  ≥2714246670.80 (0.51–1.26)0.80 (0.54–1.19)1.00 (0.61–1.66)
 Physical activity (average of three time periods,   relative units in quartiles)
  111340501.01.0
  211941551.00 (0.60–1.67)1.09 (0.69–1.74)0.92 (0.51–1.65)
  311536540.92 (0.54–1.55)1.13 (0.71–1.80)0.81 (0.45–1.48)
  411542531.08 (0.65–1.79)1.12 (0.70–1.78)0.97 (0.54–1.73)
 Caloric intake (kilocalories, in quartiles)
  <110012532481.01.0
  1100–145011341591.42 (0.82–2.44)1.53 (0.94–2.47)0.93 (0.50–1.72)
  1450–183011232511.12 (0.64–1.98)1.34 (0.82–2.19)0.84 (0.44–1.61)
  ≥183011254541.94 (1.15–3.28)1.45 (0.89–2.37)1.34 (0.73–2.46)
 Education
  High school/Technical class16045741.01.0
  Some college11642551.32 (0.81–2.14)1.06 (0.69–1.62)1.24 (0.72–2.15)
  College graduate18672831.41 (0.92–2.17)1.01 (0.69–1.49)1.39 (0.85–2.27)
 Race
  Whites3821311821.01.0
  Blacks4816240.97 (0.53–1.77)1.06 (0.63–1.78)0.92 (0.47–1.80)
  Asians and others321261.13 (0.56–2.26)0.40 (0.17–0.99)2.78 (1.02–7.61)