Table 1.
Age-adjusted baseline characteristics of participants by night-shift work duration in the Nurses’ Health Study (Women, at 1988)
| Night-shift work duration |
|||
|---|---|---|---|
| Characteristic | Never | 1 - 14 years | ≥ 15 years |
| N of participants | 31,382 | 40,359 | 5,729 |
| Age, years* | 54.7 (7.2) | 54.7 (7.1) | 54.8 (7.1) |
| Race (White), % | 97.9 | 97.5 | 96.5 |
| Body mass index, kg/m2 | 25.3 (4.8) | 25.6 (4.9) | 26.9 (5.5) |
| Family history of colorectal cancer, % | 11.4 | 11.6 | 12.1 |
| History of sigmoidoscopy / endoscopy, % | 12.4 | 12.6 | 11.4 |
| Postmenopausal status, % | 72.1 | 72.5 | 76.0 |
| Postmenopausal hormone use, % | 37.5 | 38.1 | 35.5 |
| Total activity, METS - hours/week§ | 14.6 (20.8) | 16.0 (22.0) | 16.6 (24.0) |
| Regular aspirin use (2 or more tablets/week), % | 39.3 | 40.9 | 42.6 |
| Smoking status, % | |||
| Never, % | 45.6 | 43.3 | 42.2 |
| Smoking, pack years 0 −10, % | 16.8 | 17.4 | 14.4 |
| Pack years > 10, % | 36.3 | 37.9 | 41.7 |
| Total alcohol intake, g/day | 6.2 (10.6) | 6.3 (10.7) | 5.2 (10.3) |
| Total vitamin D, IU/day | 341 (252) | 343 (253) | 337 (255) |
| Total folate intake, μg/day | 403 (221) | 407 (224) | 395 (218) |
| Total energy intake, kcal/day | 1747 (519) | 1782 (525) | 1789 (556) |
| Red meat, servings/week | 2.2 (1.4) | 2.2 (1.4) | 2.2 (1.4) |
| Processed meat, servings/week | 1.0 (1.3) | 1.0 (1.3) | 1.1 (1.3) |
| Total calcium intake, mg/day | 1093 (514) | 1088 (507) | 1056 (508) |
| Sleep duration, % | |||
| Sleep < 6h, % | 3.1 | 3.8 | 8.4 |
| Sleep 6h -< 7h, % | 20.5 | 22.4 | 28.2 |
| Sleep 7h -< 8h, % | 50.2 | 49.5 | 44.0 |
| Sleep 8h -< 9h, % | 21.9 | 20.3 | 15.7 |
| Sleep ≥ 9h, % | 4.3 | 3.9 | 3.6 |
| History of type 2 diabetes, % | 4.1 | 4.3 | 6.7 |
Values were means ± standard deviation (SD) or percentages and were standardized to the age distribution of the study population.
*
Value was not age adjusted.
§
METS, metabolic equivalent task score.