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
| 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 |
*Only available for 17,545 nurses