Crouse et al. The key differences between these meth- (i.e., approximately the 10-year period before Statistical analysis. We used uncondi- ods of adjustment is that the first is based on diagnosis). These final surfaces were created by tional logistic regression to estimate ORs and interpolated surfaces created with observed adding each 1996 surface to the correspond- associated 95% CIs. In order not to lose sub- measurements of NO2 for 2006 but uses ing 1985 surface and dividing the outcome by jects because of missing values for continuous fewer data points, whereas the second is based 2. To assess the spatial variability between all nonoccupational covariates, we used para- on interpolated surfaces created with pre- seven exposure surfaces (i.e., land-use regres- metric smoothers (natural cubic splines) in dicted estimates of NO2 for 2006 but is based sion for 2006, two extrapolated surfaces for age-adjusted logistic models to view the fitted on a greater number of data points. 1985, two extrapolated surfaces for 1996, two response functions. Based on the fitted plots, We also created two additional surfaces surfaces for 1985–1996), 1,000 randomly gen- we found cut points for each covariable that that described the mean estimates of NO2 dur- erated points were sampled and Pearson cor- defined categories such that the OR within ing the 10-year period between 1985 and 1996 relation coefficients were estimated. each category was approximately constant. Table 1. Distribution of risk factors and age-adjusted ORs and 95% CIs, postmenopausal breast cancer, Montreal, Canada (n = 799). Cases Controls Cases Controls Variable (reference category)a [n (%)] [n (%)] OR (95% CI) Variable (reference category)a [n (%)] [n (%)] OR (95% CI) Mother or sister with breast cancer 210 (54.8) 279 (67.1) 1 Body mass index (18.5 to < 25) 190 (49.6) 194 (46.6) 1 (no) 25 to < 30 123 (32.1) 133 (32.0) 0.97 (0.71–1.34) Yes 83 (21.7) 47 (11.3) 2.36 (1.58–3.52) > 30 to < 35 48 (12.5) 51 (12.3) 1.00 (0.64–1.56) No for mother, no sisters 79 (20.6) 76 (18.3) 1.40 (0.97–2.01) ≥ 35 15 (3.9) 28 (6.7) 0.54 (0.28–1.06) Missing information 11 (2.9) 14 (3.4) 1.13 (0.50–2.55) < 18.5 6 (1.6) 9 (2.2) 0.69 (0.24–1.99) Oophorectomy (never) 276 (72.1) 194 (46.6) 1 Missing information 1 (0.3) 1 (0.2) NE Only one ovary removed 27 (7) 30 (7.2) 0.61 (0.35–1.07) Tobacco exposure (none)b 45 (11.7) 52 (12.5) 1 Age at bilateral oophorectomy, years Environmental tobacco smoke only 160 (41.8) 148 (35.6) 1.17 (0.66–2.08) < 44 26 (6.8) 34 (8.2) 0.55 (0.32–0.95) Active smoker with or without 176 (46) 209 (50.2) 1.02 (0.65–1.61) 45–49 19 (5) 15 (3.6) 0.89 (0.44–1.79) exposure to environmental 50–54 16 (4.2) 26 (6.3) 0.39 (0.20–0.76) tobacco smoke ≥ 55 17 (4.4) 106 (25.5) 0.12 (0.07–0.20) Missing information 2 (0.5) 7 (1.7) NE Missing information 2 (0.5) 11 (2.6) 0.13 (0.03–0.59) Respondent (self) 362 (94.5) 362 (87) 1 Education, years (≤ 7) 107 (27.9) 154 (37) 1 Proxy 21 (5.5) 54 (13) 0.41 (0.24–0.69) Alcohol status (never drinker)c 8–10 78 (20.4) 107 (25.7) 1.05 (0.72–1.54) 193 (50.4) 229 (55) 1 11–17 178 (46.5) 138 (33.2) 1.82 (1.30–2.53) Former drinker 50 (13.1) 55 (13.2) 1.01 (0.66–1.57) ≥ 18 20 (5.2) 17 (4.1) 1.58 (0.78–3.17) Infrequent drinker 53 (13.8) 53 (12.7) 1.15 (0.75–1.76) Ethnicity (French) 232 (60.6) 219 (52.6) 1 Current drinker 87 (22.7) 79 (19) 1.26 (0.88–1.81) English and others 98 (25.6) 110 (26.4) 0.86 (0.62–1.20) Benign breast disease (no) 197 (51.4) 333 (80) 1 Jewish and Italian 53 (13.8) 87 (20.9) 0.58 (0.39–0.86) Yes 185 (48.3) 83 (20) 3.71 (2.70–5.08) Age at menarche, years (≥ 16) 24 (6.3) 39 (9.4) 1 Missing information 1 (0.3) 0 (0) NE 14–15 97 (25.3) 109 (26.2) 1.47 (0.82–2.62) Occupational exposure to solvents 338 (88.3) 374 (89.9) 1 13 110 (28.7) 100 (24) 1.82 (1.02–3.24) with reactive metabolites (not exposed)d 12 78 (20.4) 98 (23.6) 1.28 (0.71–2.30) ≤ 11 74 (19.3) 70 (16.8) 1.65 (0.90–3.02) Nonsubstantial, 5 years 5 (1.3) 4 (1) 1.35 (0.36–5.09) Age at first full-term pregnancy, 83 (21.7) 77 (18.5) 1 Substantial, 5 years 6 (1.6) 5 (1.2) 1.26 (0.38–4.17) years (never) Exposed only at R = 1 12 (3.1) 9 (2.2) 1.43 (0.60–3.45) < 18 15 (3.9) 12 (2.9) 1.12 (0.49–2.55) Other exposures 22 (5.7) 24 (5.8) 0.99 (0.55–1.81) ≥ 18 to 26 166 (43.3) 214 (51.4) 0.71 (0.49–1.04) Occupational exposure to extremely 81 (21.1) 102 (24.5) 1 low magnetic fields (not exposed)d > 26 to 30 59 (15.4) 56 (13.5) 1.00 (0.62–1.62) > 30 46 (12) 36 (8.7) 1.24 (0.72–2.12) Nonsubstantial, 5 years 107 (27.9) 96 (23.1) 1.30 (0.86–1.97) Pregnant but never full term 14 (3.7) 21 (5) 0.59 (0.28–1.24) Substantial, 5 years 48 (12.5) 44 (10.6) 1.30 (0.78–2.17) Breast-feeding, duration, weeks (0) 296 (77.3) 303 (72.8) 1 Exposed only at R = 1 8 (2.1) 18 (4.3) 0.57 (0.24–1.37) 0–80 69 (18) 77 (18.5) 0.93 (0.65–1.34) Other exposures 139 (36.3) 156 (37.5) 1.06 (0.73–1.55) > 80 18 (4.7) 36 (8.7) 0.53 (0.30–0.96) Occupational exposure to carbon 299 (78.1) 339 (81.5) 1 monoxide (not exposed)d Years of oral contraception use 248 (64.8) 290 (69.7) 1 (never) Nonsubstantial, 5 years 36 (9.4) 21 (5.0) 1.87 (1.07–3.27) < 1 42 (11) 25 (6) 1.78 (1.04–3.05) Substantial, 5 years 0 (0.0) 0 (0.0) NE ≥ 1 93 (24.3) 101 (24.3) 0.96 (0.67–1.38) Exposed only at R = 1 1 (0.3) 1 (0.2) 1.18 (0.07–19.10) Hormone replacement therapy, 170 (44.4) 236 (56.7) 1 Other exposures 47 (12.3) 55 (13.2) 0.94 (0.62–1.43) months (0) Occupational exposure to polycyclic 354 (92.4) 386 (92.8) 1 1–19 53 (13.8) 57 (13.7) 1.28 (0.84–1.95) aromatic hydrocarbons from petroleum (not exposed)d 20–44 29 (7.6) 34 (8.2) 1.14 (0.67–1.96) Nonsubstantial, 5 years 9 (2.3) 4 (1.0) 2.34 (0.72–7.63) 45–74 35 (9.1) 21 (5) 2.19 (1.23–3.92) Substantial, 5 years 2 (0.5) 2 (0.5) 1.07 (0.15–7.69) 75–99 16 (4.2) 13 (3.1) 1.58 (0.73–3.39) Exposed only at R = 1 2 (0.5) 8 (1.9) 0.28 (0.64–1.22) ≥ 100 80 (20.9) 55 (13.2) 1.98 (1.33–2.95) Other exposures 16 (4.2) 16 (3.8) 1.03 (0.51–2.10) NE, not estimated. aCategories shown are those modeled in the analyses (see Table 3); reference group for each category is in parentheses. bThis variable was compiled with information acquired from several questions. Subjects were asked if they had smoked 100 cigarettes over the course of their lifetime, along with follow-up questions, to determine whether they were former, current, or never-smokers. Subjects were also asked whether they had ever been exposed to residential or occupational environmental tobacco smoke, along with follow-up ques- tions concerning duration and kind of exposure. cThe categories for this variable were determined based on information from several questions. Subjects were asked whether there had ever been a time in their life when they had consumed one or more drinks of beer, wine, or liquor (respectively) on a monthly basis, or on a weekly basis. dSubstantial exposure, ≥ 5 years of exposure at medium or high levels of intensity; nonsubstantial exposure, < 5 years of exposure at medium or high levels of intensity, but still ≥ 5 years of exposure at any inten- sity; exposed only at R = 1, exposure only at the lowest level of confidence; other exposures, exposures totaling < 5 years. 1580 118 | number 11 | November 2010 • Environmental Health Perspectives ovlume