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Table 1 Descriptive statistics at the cohort baseline (1993 or 1999) among 22,466 female nurses from the Danish Nurse Cohort by breast cancer status at the end of follow up

From: Long-term exposure to road traffic noise and incidence of breast cancer: a cohort study

  Total Breast cancer No breast cancer
N = 22,466 N = 1193 N = 21,273
Age, mean (SD) 53.0 ± 7.9 53.6 ± 7.5 53.0 ± 7.9
Birth cohort
  < 1935, n (%) 5067 (22.6) 290 (24.3) 4777 (22.5)
 1935–1944, n (%) 6878 (30.6) 446 (37.4) 6432 (30.2)
 1945–1949, n (%) 4738 (21.1) 250 (21.0) 4488 (21.1)
  ≥ 1950, n (%) 5783 (25.7) 207 (17.4) 5576 (26.2)
Body mass index (BMI), mean (SD) 23.7 ± 3.5 23.8 ± 3.5 23.7 ± 3.5
 BMI < 18.5 kg/m2, n (%) 544 (2.4) 24 (2.0) 520 (2.4)
 BMI 18.5–24.9 kg/m2, n (%) 15,463 (68.8) 845 (70.8) 14,618 (68.7)
 BMI 25–29.9 kg/m2, n (%) 5161 (23.0) 247 (20.7) 4914 (23.1)
 BMI > 30 kg/m2, n (%) 1298 (5.8) 77 (6.5) 1221 (5.7)
Physical activity
 Low, n (%) 1466 (6.5) 79 (6.6) 1387 (6.5)
 Medium, n (%) 14,944 (66.5) 806 (67.6) 14,138 (66.5)
 High, n (%) 6056 (27.0) 308 (25.8) 5748 (27.0)
Smoking status
 Never, n (%) 7907 (35.2) 372 (31.2) 7535 (35.4)
 Previous, n (%) 6901 (30.7) 356 (29.8) 6545 (30.8)
 Current, n (%) 7658 (34.1) 465 (39.0) 7193 (33.8)
Alcohol consumption, mean (SD) 114.6 ± 128.1 123.2 ± 125.1 114.1 ± 128.2
 Does not drink alcohol, n (%) 3444 (15.3) 189 (15.8) 3255 ± 15.3
 Moderate drinker (1–14 drinks/week), n (%) 13,909 (61.9) 689 (57.8) 13,220 (62.1)
 Heavy drinker (> 14 drinks/week), n (%) 5113 (22.8) 315 (26.4) 4798 (22.6)
Age at menarche
  ≥ 12, n (%) 5431 (24.2) 301 (25.2) 5130 (24.1)
  < 12, n (%) 17,035 (75.8) 892 (74.7) 16,143 (75.9)
Parity
 Nulliparous, n (%) 3165 (14.1) 192 (16.1) 2973 (14.0)
 Parous, n (%) 19,301 (85.9) 1001 (83.9) 18,300 (86.0)
Number of births in parous women, mean (SD) 2.34 ± 0.88 2.31 ± 0.88 2.34 ± 0.88
Age at first birth, mean (SD) 25.9 ± 3.96 26.2 ± 4.11 25.9 ± 3.95
Menopausal status
 Premenopausal, n (%) 11,388 (50.7) 596 (50.0) 10,792 (50.7)
 Post-menopausal, n (%) 11,078 (49.3) 597 (50.0) 10,481 (49.3)
Use of hormone therapy
 Never, n (%) 16,389 (73.0) 774 (64.9) 15,615 (73.4)
 Previous, n (%) 2193 (9.8) 109 (9.1) 2084 (9.8)
 Current, n (%) 3884 (17.3) 310 (26.0) 3574 (16.8)
Night work*
 Yes, n (%) 947 (5.4) 47 (5.1) 900 (5.4)
 No, n (%) 16,598 (94.6) 873 (94.9) 15,725 (94.6)
Use of oral contraceptives
 Never, n (%) 9244 (41.1) 510 (42.7) 8734 (41.1)
 Previous or current, n (%) 13,222 (58.9) 683 (57.3) 12,539 (58.9)
Residential area
 Urban, n (%) 3367 (15.0) 173 (14.5) 3194 (15.0)
 Provincial, n (%) 9711 (43.2) 549 (46.0) 9162 (43.1)
 Rural, n (%) 9388 (41.8) 471 (39.5) 8917 (41.9)
Road traffic noise levels at baseline residence
 Lden, mean (SD) 52.7 ± 8.2 53.0 ± 8.1 52.7 ± 8.2
 LA24h, mean (SD) 48.6 ± 8.2 48.9 ± 8.1 48.6 ± 8.2
 Ld, mean (SD) 50.4 ± 8.2 50.7 ± 8.2 50.4 ± 8.2
 Le, mean (SD) 48.1 ± 8.1 48.4 ± 8.1 48.1 ± 8.1
 Ln, mean (SD) 44.6 ± 8.0 44.8 ± 8.0 44.5 ± 8.0
  1. *Only available for 17,545 nurses