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Table 1 Distribution of select baseline characteristics among invasive breast cancer (BC) cases and non-cases included in the present analysis [ n (%)]

From: Hazardous air pollutants and breast cancer risk in California teachers: a cohort study

Characteristics Non-cases BC cases
Total 106,702 (100) 5,676 (100)
Race/ethnicity   
 White 91,831 (86.1) 5,061 (89.2)
 Black 2,894 (2.7) 134 (2.4)
 Hispanic 4,805 (4.5) 153 (2.7)
 Asian/Pacific Islander 3,907 (3.7) 193 (3.4)
 Other/Mixed 3,265 (3.1) 135 (2.4)
Age group (years)   
 20-29 5,212 (4.9) 42 (0.7)
 30-39 14,906 (14.0) 276 (4.9)
 40-49 28,880 (27.1) 1,268 (22.3)
 50-59 25,562 (24.0) 1,800 (31.7)
 60-69 16,655 (15.6) 1,363 (24.0)
 70-79 10,807 (10.1) 749 (13.2)
 ≥80 4,680 (4.4) 178 (3.1)
Family history of breast cancer (first degree relative)
 Yes 12,221 (11.5) 965 (17.0)
 No 90,390 (84.7) 4,504 (79.4)
 Missing/Adopted 4,091 (3.8) 207 (3.7)
Age (years) at menarche   
 ≤11 23,558 (22.1) 1,350 (23.8)
 12-13 59,732 (56.0) 3,137 (55.3)
 ≥14 21,746 (20.4) 1,109 (19.5)
 Missing/Never 1,666 (1.6) 80 (1.4)
Age (years) at first full-term pregnancy  
 ≤24 27,115 (25.4) 1,522 (26.8)
 25-29 31,105 (29.2) 1,753 (30.9)
 ≥30 18,110 (17.0) 987 (17.4)
 Nulliparous* 28,229 (26.5) 1,310 (23.1)
 Missing 2,143 (2.0) 104 (1.8)
Duration of breastfeeding (months)   
 Pregnant, no live births 6,248 (5.9) 272 (4.8)
 Never 16,977 (15.9) 1,092 (19.2)
 <6 18,615 (17.5) 1,030 (18.2)
 6-11 14,378 (13.5) 769 (13.6)
 ≥12 25,978 (24.4) 1,356 (23.9)
 Nulliparous 21,849 (20.5) 1,036 (18.3)
 Missing 2,657 (2.5) 121 (2.1)
BMI (mg/m 2 )   
 <25 62,747 (58.8) 3,123 (55.0)
 25-29 25,091 (23.5) 1,517 (26.7)
 ≥30 14,206 (13.3) 794 (14.0)
 Outlier/Unknown 4,658 (4.4) 242 (4.3)
Physical activity (hours/week)   
 ≤0.50 31,771 (29.8) 2,028 (35.7)
 0.51-2.00 33,993 (31.9) 1,801 (31.7)
 2.01-3.50 18,709 (17.5) 876 (15.4)
 3.51-5.00 10,155 (9.5) 482 (8.5)
 >5.00 11,295 (10.6) 438 (7.7)
 Missing/Unknown 779 (0.7) 51 (0.9)
Menopausal status   
 Premenopausal 44,158 (41.4) 1,405 (24.8)
 Perimenopausal 2,140 (2.0) 143 (2.5)
 Postmenopausal 51,819 (48.6) 3,604 (63.5)
 Missing 8,585 (8.1) 524 (9.2)
Hormone therapy use   
 Past/never 18,796 (17.6) 1,052 (18.5)
 Current 27,566 (25.8) 2,204 (38.8)
 Other (pre/peri) 60,340 (56.6) 2,420 (42.6)
Alcohol consumption (g/day)   
 None 34,278 (32.1) 1,663 (29.3)
 <20 58,433 (54.8) 3,139 (55.3)
 ≥20 8,084 (7.6) 594 (10.5)
 Missing 5,907 (5.5) 280 (4.9)
Smoking status   
 Never 71,010 (66.6) 3,338 (58.8)
 Former 29,656 (27.8) 1,938 (34.1)
 Current 5,349 (5.0) 351 (6.2)
 Missing 687 (0.6) 49 (0.9)
Total pack-years of smoking  
 Never smokers 71,010 (66.6) 3,338 (58.8)
 ≤10 17,257 (16.2) 988 (17.4)
 11-20 5,961 (5.6) 416 (7.3)
 21-30 3,491 (3.3) 280 (4.9)
 ≥31 5,182 (4.9) 417 (7.4)
 Missing/Unknown 3,801 (3.6) 237 (4.2)
Moving status   
 Non-mover 55,496 (52.0) 3,496 (61.6)
Year of diagnosis   
 1995-2001 2,384 (42.0)
 2002-2011 3,292 (58.0)
Tumor hormone responsive   
 Estrogen-receptor positive (ER+) 4,293 (75.6)
 Progesterone-receptor positive (PR+) 3,477 (61.3)
 ER+ or PR+ 4,352 (76.7)
 ER- and PR- 704 (12.4)
  1. *Includes nulliparous women who were 1) pregnant without a live birth or 2) whose breast feeding history is unknown.