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Table 1 Distribution of baseline characteristics for 4,769 women from Diet, Cancer, and Health cohort

From: Long-term exposure to air pollution and mammographic density in the Danish Diet, Cancer and Health cohort

  Total N = 4,769 Mammographic density
Mixed/dense N = 2,705 Fatty N = 2,064
Baseline characteristics    
Mean (SD) age (years) 56.2 (4.4) 55.4 (4.3) 57.2 (4.4)
Menopausal, n (%) 3,930 (82.4) 2,147 (79.4) 1,783 (86.4)
Mean (SD) BMI (kg/m2) 25.9 (4.7) 24.6 (3.9) 27.6 (5.1)
Obese, n (%) 792 (16.6) 249 (9.2) 543 (26.3)
Short education (≤7 years), n (%) 1660 (34.8) 816 (30.2) 844 (40.9)
Medium education (8–10 years), n (%) 2355 (49.4) 1369 (50.6) 986 (47.8)
Long education (>10 years), n (%) 754 (15.8) 520 (19.2) 234 (11.3)
Alcohol use, n (%) 4,610 (96.7) 2623 (97.0 ) 1987 (96.3)
Mean (SD) alcohol use in users (g/day) 13.9 (16.6) 14.8 (16.4) 12.8 (16.8)
Never smoked, n (%) 1814 (38.0) 1025 (37.9) 789 (38.2)
Previously smoked, n (%) 993 (20.8) 548 (20.3) 445 (21.6)
Current smoker, n (%) 1962 (41.1) 1132 (41.8) 830 (40.2)
Mean (SD) duration of smoking in ever smokers (years) 30.2 (11.8) 29.4 (11.6) 31.1 (11.9)
Mean (SD) smoking intensity in ever smokers (g/day) 10.0 (9.6) 10.2 (9.7) 9.7 (9.4)
Physically active, n (%) 2370 (49.7) 1384 (51.2) 986 (47.8)
Nulliparious, n (%) 662 (13.9) 455 (16.8) 207 (10.0)
History of benign breast tumor, n(%) 603 (12.6) 429 (15.9) 174 (8.4)
Ever used HRT 2295 (48.1) 1,398 (51.7) 897 (43.5)
Mean (SD) duration of HRT use in ever users (years) 5.6 (6.2) 5.6 (6.2) 5.6 (6.2)
Air pollution exposure at residential address    
Mean (SD) baseline NOx (1-year mean 1993/97) 46.1 (42.4) 45.7 (41.5) 46.7 (43.5)
Mean (SD) NOx since 1971 (ca. 25-year mean 1971-1993/97) 41.5 (30.7) 41.0 (30.0) 42.1 (31.6)
Mean (SD) baseline NO2 (1-year mean 1993/97) 23.0 (8.3) 23.0 (8.2) 23.1 (8.4)
Mean (SD) NO2 since 1971 (ca. 25-year mean 1971-1993/97) 21.2 (6.2) 21.1 (6.0) 21.3 (6.3)
  1. SD - standard deviation, BMI - body mass index, HRT- hormone replacement therapy.