Skip to main content

Table 1 Characteristic of the study population (n = 279,967), by breast density category (number [percentage])

From: Association between air pollution and mammographic breast density in the Breast Cancer Surveilance Consortium

Characteristics Almost entirely fat (BI-RADS I) n = 30,249 Scattered fibroglandular densities (BI-RADS II) n = 116,666 Heterogeneously dense (BI-RADS III) n = 110,181 Extremely dense (BI-RADS IV) n = 22,871
Age at mammogram, years
 40–49 4526 (15.0) 27,195 (23.3) 38,172 (34.6) 11,261 (49.2)
 50–59 9548 (31.6) 37,768 (32.4) 37,004 (33.6) 7432 (32.5)
 60–69 8749 (28.9) 28,004 (24.0) 19,960 (18.1) 2536 (11.1)
 70–79 5388 (17.8) 16,712 (14.3) 10,331 (9.4) 1069 (4.7)
 80–89 2038 (6.7) 6987 (6.0) 4714 (4.3) 573 (2.5)
Race/ethnicity
 White 25,879 (85.6) 101,078 (86.6) 92,698 (84.1) 18,170 (79.4)
 Black 703 (2.3) 2031 (1.7) 1873 (1.7) 352 (1.5)
 Asian/Pacific Islander 842 (2.8) 4085 (3.5) 7416 (6.7) 2662 (11.6)
 American Indian 117 (0.4) 442 (0.4) 373 (0.3) 45 (0.2)
 Hispanic 2056 (6.8) 6248 (5.4) 5122 (4.6) 1115 (4.9)
 Mixed/other 652 (2.2) 2782 (2.4) 2699 (2.4) 527 (2.3)
Body mass index, kg/m2
 ≤18.4 142 (0.5) 956 (0.8) 1808 (1.6) 1198 (5.2)
 18.5–24.9 5383 (17.8) 36,175 (31.0) 53,604 (48.7) 15,974 (69.8)
 25.0–29.9 8846 (29.2) 38,576 (33.1) 33,316 (30.2) 4283 (18.7)
 30.0–34.9 7548 (25.0) 23,267 (19.9) 13,803 (12.5) 1038 (4.5)
 35.0–39.9 4361 (14.4) 10,501 (9.0) 5028 (4.6) 273 (1.2)
 ≥40 3969 (13.1) 7191 (6.2) 2622 (2.4) 105 (0.5)
Age at menarche, years
 ≤12 14,400 (47.6) 51,281 (44.0) 44,093 (40.0) 7989 (34.9)
 13 9211 (30.5) 37,191 (31.9) 35,622 (32.3) 7516 (32.9)
 14 3626 (12.0) 15,203 (13.0) 15,816 (14.4) 3682 (16.1)
 ≥15 3012 (10.0) 12,991 (11.1) 14,650 (13.3) 3684 (16.1)
Parity/age at first child
 Nulliparous 4019 (13.3) 14,264 (12.2) 18,085 (16.4) 5727 (25.0)
 Parous/≤29 years 23,317 (77.1) 88,215 (75.6) 74,309 (67.4) 11,896 (52.0)
 Parous/≥30 years 2913 (9.6) 14,187 (12.2) 17,787 (16.1) 5248 (22.9)
Menopausal status/HRT
 Premenopausal 3776 (12.5) 24,161 (20.7) 35,502 (32.2) 10,855 (47.5)
 Postmenopausal/current HRT use 3064 (10.1) 14,627 (12.5) 15,995 (14.5) 2840 (12.4)
 Postmenopausal/no current HRT use 22,908 (75.7) 75,358 (64.6) 55,548 (50.4) 8378 (36.6)
 Perimenopausal 501 (1.7) 2520 (2.2) 3136 (2.8) 798 (3.5)
Family history of breast cancer
 Yes 5099 (16.9) 19,787 (17.0) 18,946 (17.2) 3860 (16.9)
 No 25,150 (83.1) 96,879 (83.0) 91,235 (82.8) 19,011 (83.1)
History of breast biopsy
 Yes 5250 (17.4) 23,387 (20.0) 26,687 (24.2) 6255 (27.3)
 No 24,999 (82.6) 93,279 (80.0) 83,494 (75.8) 16,616 (72.7)
Residential area
 Urban 17,673 (59.1) 63,393 (54.6) 72,210 (65.6) 14,933 (65.4)
 Rural 12,244 (40.9) 52,816 (45.4) 37,794 (34.4) 7916 (34.6)
Median household income
 ≤US$46,075 8811 (29.1) 33,011 (28.3) 24,474 (22.2) 4591 (20.1)
 US$46,076–54,093 7871 (26.0) 31,185 (26.7) 25,607 (23.2) 5324 (23.3)
 US$54,094–66,322 7051 (23.3) 28,168 (24.1) 30,237 (27.4) 5897 (25.8)
 ≥US$66,323 6516 (21.5) 24,302 (20.8) 29,863 (27.1) 7059 (30.9)
PM2.5 (ug/m3)
 Mean (SD) 8.77 8.88 9.24 9.34
 Range 2.86–19.63 2.39–19.83 2.19–23.05 2.54–18.57
Ozone (ppb)
 Mean (SD) 35.95 35.22 34.04 33.72
 Range 24.54–53.65 22.30–57.39 24.54–54.22 25.46–50.81
  1. Abbreviations: BI-RADS American College of Radiology’s Breast Imaging-Reporting and Data System; HRT hormone replacement therapy, PM 2.5 particulate matter <2.5 μm in diameter