Table 1.
Age‐standardized characteristics of the study population by rotating night shift work duration at baseline in the Nurses’ Health Study (NHS) and NHS2 (NHS: 1988, NHS2: 1989)
| NHS (N = 77,439) | NHS2 (N = 113,371) | |||||||
|---|---|---|---|---|---|---|---|---|
| No. of years worked on rotating night shifts | No. of years worked on rotating night shifts | |||||||
| Never | 1–14 | 15–29 | 30+ | Never | 1–5 | 6–14 | 15+ | |
| Characteristic | N = 31,369 | N = 40,342 | N = 4,373 | N = 1,355 | N = 43,071 | N = 55,377 | N = 13,701 | N = 1,222 |
| Age, y; mean (SD) | 54.3 (7.2) | 54.7 (7.1) | 56.1 (6.9) | 60.4 (4.6) | 34.8 (4.7) | 34.5 (4.8) | 35.5 (4.0) | 39.2 (2.5) |
| Height, inches; mean (SD) | 64.5 (2.4) | 64.5 (2.4) | 64.5 (2.5) | 64.5 (2.5) | 64.9 (2.6) | 64.9 (2.6) | 64.9 (2.7) | 64.8 (2.7) |
| BMI, kg/m2; mean (SD) | 25.3 (4.8) | 25.6 (4.9) | 26.9 (5.5) | 26.6 (5.2) | 23.9 (4.9) | 24.0 (5.0) | 24.9 (5.6) | 26.2 (6.9) |
| Obese (BMI > 30) (%) | 14 | 16 | 24 | 24 | 11 | 11 | 15 | 20 |
| Nurse's education level bachelor's or higher (%)1 | 31 | 30 | 24 | 22 | – | – | – | – |
| Husband's education level college or higher (%)2 | 54 | 56 | 41 | 49 | 80 | 83 | 80 | 82 |
| Nulliparous (%) | 5 | 6 | 6 | 6 | 26 | 29 | 34 | 39 |
| Postmenopausal (%) | 67 | 68 | 70 | 86 | 2 | 2 | 3 | 3 |
| Current menopausal hormone therapy use (%)3 | 35 | 35 | 29 | 29 | 82 | 79 | 80 | 74 |
| First‐degree family history of colorectal cancer (%) | 12 | 12 | 12 | 16 | 4 | 4 | 5 | 4 |
| Current smoker (%) | 17 | 19 | 25 | 25 | 12 | 13 | 17 | 24 |
| Pack‐years smoked; mean (SD)4 | 23.0 (19.5) | 23.2 (19.4) | 26.1 (20.0) | 26.3 (20.1) | 11.3 (8.2) | 11.2 (8.2) | 11.7 (8.1) | 13.1 (8.0) |
| Physical activity, MET‐hours/week; mean (SD) | 14.7 (20.8) | 16.0 (22.0) | 16.1 (21.7) | 19.3 (28.4) | 22.8 (34.2) | 25.8 (37.6) | 27.7 (40.1) | 40.8 (61.9) |
| Alcohol consumption, grams/day; mean (SD) | 6.2 (10.7) | 6.3 (10.7) | 5.3 (10.4) | 5.5 (9.7) | 3.0 (6.0) | 3.2 (6.2) | 3.1 (5.9) | 3.3 (8.2) |
| Total energy intake (kcal/day); mean (SD) | 1747 (519) | 1782 (525) | 1790 (556) | 1780 (560) | 1771 (540) | 1799 (549) | 1810 (568) | 1855 (534) |
| Red or processed meat, servings/day; mean (SD) | 0.5 (0.3) | 0.5 (0.3) | 0.5 (0.3) | 0.5 (0.3) | 0.8 (0.6) | 0.8 (0.6) | 0.8 (0.6) | 0.8 (0.7) |
| Folate, ug/day; mean (SD) | 402.9 (221.2) | 406.6 (223.7) | 392.5 (211.4) | 412.9 (269.0) | 475.2 (293.8) | 480.6 (292.0) | 478.1 (288.0) | 515.9 (268.5) |
| Fiber, g/day; mean (SD) | 17.6 (5.3) | 17.8 (5.4) | 17.5 (5.1) | 18.5 (6.4) | 4.8 (1.6) | 4.9 (1.6) | 4.9 (1.6) | 5.1 (1.7) |
| Current aspirin use (>2 tablets/week) (%) | 33 | 33 | 35 | 35 | 11 | 11 | 12 | 10 |
| Current NSAIDS use (>2 tablets/week) (%) | 18 | 19 | 21 | 21 | 18 | 20 | 23 | 19 |
| Colonoscopy/sigmoidoscopy in the last 2 years (%) | 6 | 6 | 5 | 5 | 2 | 2 | 2 | 1 |
1
Nurse's education level.
2
Among married or widowed women.
3
Among postmenopausal women.
4
Among smokers.