Table 1.

Age-adjusted baseline characteristics of participants by night-shift work duration in the NHS (women, at 1988).

Night-shift work duration
CharacteristicsNever1–14 years≥15 years
N of participants31,38240,3595,729
Age, yearsa54.7 (7.2)54.7 (7.1)54.8 (7.1)
Race (White), %97.997.596.5
BMI, kg/m225.3 (4.8)25.6 (4.9)26.9 (5.5)
Family history of colorectal cancer, %11.411.612.1
History of sigmoidoscopy/endoscopy, %12.412.611.4
Postmenopausal status, %72.172.576.0
Postmenopausal hormone use, %37.538.135.5
Total activity, METS—hours/week14.6 (20.8)16.0 (22.0)16.6 (24.0)
Regular aspirin use (2 or more tablets/week), %39.340.942.6
Smoking status, %
 Never, %45.643.342.2
 Smoking‚ pack-years 0–10, %16.817.414.4
 Pack-years >10, %36.337.941.7
Total alcohol intake, g/day6.2 (10.6)6.3 (10.7)5.2 (10.3)
Total vitamin D, IU/day341 (252)343 (253)337 (255)
Total folate intake, μg/day403 (221)407 (224)395 (218)
Total energy intake, kcal/day1,747 (519)1,782 (525)1,789 (556)
Red meat, servings/week2.2 (1.4)2.2 (1.4)2.2 (1.4)
Processed meat, servings/week1.0 (1.3)1.0 (1.3)1.1 (1.3)
Total calcium intake, mg/day1,093 (514)1,088 (507)1,056 (508)
Sleep duration, %
 Sleep <6 h, %3.13.88.4
 Sleep 6 h–<7 h, %20.522.428.2
 Sleep 7 h–<8 h, %50.249.544.0
 Sleep 8 h–<9 h, %21.920.315.7
 Sleep ≥9 h, %4.33.93.6
History of type II diabetes, %4.14.36.7
  • Note: Values were means ± SD or percentages and were standardized to the age distribution of the study population.

  • Abbreviation: METS, metabolic equivalent task score.

  • aValue was not age adjusted.