BMC Cancer 2008, 8:157 http://www.biomedcentral.com/1471-2407/8/157 Table 3: Secondhand smoke exposure at work and breast cancer among non-smoking cases and controls from Delaware Secondhand smoke exposure at worka cases controls odds ratiob 95% confidence Intervalb Never employed or not exposed at work Any secondhand smoke exposure at work Number of years employed at a job with secondhand smoke exposure < 10 10–19 20–45 Number of years employed at a job with light secondhand smoke exposure < 10 ≥ 10 Number of years employed at a job with moderate secondhand smoke exposure < 10 ≥ 10 Number of years employed at a job with heavy secondhand smoke exposure < 10 ≥ 10 n % n % 60 48.4 69 43.4 64 51.6 90 56.6 27 21.8 48 30.1 24 19.4 27 17.0 13 10.5 15 9.4 17 13.7 27 17.0 13 10.5 13 8.2 11 8.9 16 10.1 17 13.7 22 13.8 5 7 4.0 5.6 8 7 5.0 4.4 1.00 0.80 0.66 1.02 0.86 0.96 1.14 0.70 1.01 1.02 1.07 Reference 0.49–1.32 0.35–1.23 0.52–2.00 0.35– 2.07 0.46–1.97 0.47– 2.78 0.29– 1.68 0.49– 2.09 0.31– 3.37 0.35– 3.30 a 2 non-smoking controls were missing data on exposure to smoke at work b Adjusted for age, menopausal status, body mass index (<25, 25–29, 30+), age at menarche (<12 vs. 12+), age at first live birth (nulliparous, <30, 30+), oral contraceptive use (ever vs. never), other hormone use (ever vs. never), family history of breast cancer (yes vs. no), alcohol consumption (ever drank 12 drinks in lifetime vs. had 12 drinks in lifetime but never had 1+ drink per month for 6+ months vs. ever had 1+ drink per month for 6+ months); data for adjustment factors was missing for 4 cases and 3 controls Table 4: Active smoking and breast cancer among cases and controls from Delaware, using women never exposed to active or secondhand smoking as the reference group Active cigarette smoking exposure Unexposed definition # 1a Definition # 2 Definition # 3 Unexposed to active and secondhand smokea Definition # 1 Definition # 2 Definition # 3 Ever active smoker Years of smokingb < 20 20–39 ≥ 40 Cigarettes per dayc < 10 10–19 ≥ 20 Pack-yearsc < 10 10–29 ≥ 30 Any exposure before age 18 Any exposure before first live birth cases controls ORb 95% CIb ORb 95% CIb ORb 95% CIb 13 30 41 163 50 70 42 58 67 34 56 65 38 109 120 14 37 46 150 59 58 33 49 58 41 54 55 39 106 127 1.00 1.21 0.98 1.31 1.35 1.31 1.30 0.90 1.20 1.30 1.03 1.13 1.06 reference 0.55–2.66 0.42–2.31 0.57–3.02 0.55–3.32 0.56–3.08 0.56–3.00 0.37–2.18 0.51–2.81 0.56–3.01 0.43–2.49 0.51–2.52 0.48–2.35 1.00 1.33 1.10 1.45 1.48 1.45 1.44 0.99 1.34 1.43 1.13 1.27 1.18 reference 0.77–2.27 0.59–2.05 0.80–2.63 0.74–2.96 0.78–2.71 0.79–2.63 0.51–1.94 0.72–2.48 0.78–2.63 0.58–2.20 0.73–2.21 0.68–2.04 1.00 1.23 1.03 1.35 1.31 1.33 1.33 0.91 1.25 1.32 1.02 1.18 1.08 reference 0.76–1.98 0.58–1.82 0.77–2.36 0.69–2.47 0.75–2.35 0.76–2.32 0.49–1.69 0.70–2.21 0.75–2.31 0.55–1.89 0.71–1.95 0.66–1.76 a Women unexposed to secondhand smoke were defined as follows: Definition #1: Zero years lifetime residential and occupational exposure; Definition #2: ≤ 10 years lifetime residential exposure, ≤ 10 years of moderate-level occupational exposure and ≤ 10 years heavy-level occupational exposure; Definition #3: Zero years of residential exposure before age 18 b OR, odds ratio; CI, confidence interval; adjusted for age and menopausal status c Data missing on total years smoked for 1 case, and cigs/day and pack-years for 4 cases and 2 controls Page 6 of 9 (page number not for citation purposes)