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Table 2 Active smoking and breast cancer among cases and controls, Delaware, 2000–2002

From: Case-control study of tobacco smoke exposure and breast cancer risk in Delaware

  cases controls odds ratioa 95% confidence intervala
Active smoke exposure n % n %   
Ever smoked 100 cigarettes       
   No 124 43.2 161 51.8 1.00 reference
   Yes 163 56.8 150 48.2 1.43 1.03–1.99
Total years smoked cigarettesb       
   <10 23 8.0 26 8.4 1.36 0.72–2.55
   10–19 27 9.4 33 10.6 1.13 0.64–2.01
   20–29 34 11.9 26 8.4 1.80 1.02–3.20
   30–39 36 12.6 32 10.3 1.31 0.76–2.25
   40–49 27 9.4 21 6.8 1.50 0.79–2.82
   50–62 15 5.2 12 3.9 1.21 0.52–2.84
Average number of cigarettes/dayb       
   <10 58 20.5 49 15.9 1.60 1.01–2.53
   10–19 67 23.7 58 18.8 1.53 0.99–2.35
   20–29 25 8.8 29 9.4 1.12 0.61–2.04
   30–68 9 3.2 12 3.9 0.84 0.34–2.08
Total pack-yearsb       
   <5 37 13.1 36 11.7 1.45 0.85–2.45
   5–9 19 6.7 18 5.8 1.65 0.81–3.35
   10–19 37 13.1 26 8.4 1.83 1.04–3.23
   20–29 28 9.9 29 9.4 1.24 0.69–2.24
   30–39 10 3.5 12 3.9 1.06 0.44–2.56
   40–49 16 5.7 9 2.9 1.92 0.81–4.55
   50–102 12 4.2 18 5.8 0.75 0.34–1.65
Years smoked at or before age 18c       
   <5 93 32.4 91 29.3 1.34 0.91–1.96
   5–10 16 5.6 15 4.8 1.33 0.62–2.85
Years smoked, before first live birthd       
   Never smokers 108 37.6 138 44.4 1.00 reference
   <5 38 13.2 36 11.6 1.25 0.73–2.13
   5–9 59 20.6 55 17.7 1.37 0.87–2.16
   10–14 12 4.2 27 8.7 0.69 0.33–1.45
   15–39 11 3.8 9 2.9 1.99 0.76–5.18
  1. a adjusted for age, education, and menopausal status
  2. b Numbers do not always total due to missing data
  3. c Excludes women who smoked only after age 18
  4. d Excludes nulliparous women and those who smoked only after the birth of their first child