Table 1.
Age and age-adjusted characteristics of 32,470 women in the Nurses’ Health Study II by chronotype at baseline (2009). yr = year, h=hour, MET = Metabolic Equivalent of Task. Values are either mean (standard deviation) or percentages.
| Early type | Intermediate type | Late type | |
|---|---|---|---|
| Sample Size | 12,261 | 17,073 | 3,136 |
|
| |||
| Age, yr | 55.0 (4.6) | 55.0 (4.7) | 55.0 (4.7) |
| Married or with partner | 85 | 84 | 78 |
| Living alone, % | 9 | 9 | 14 |
| Household income (census-tract level) | 66,626 (24,545) | 66,413 (24,127) | 66,135 (23,392) |
| Retired (yes), % | 18 | 17 | 20 |
| Smoking status, % | |||
| Never smoker | 70 | 70 | 66 |
| Past smoker | 26 | 26 | 27 |
| Current smoker | 4 | 4 | 7 |
| Pack-years of smoking1 | 29.1 (15.2) | 27.9 (14.8) | 32.0 (16.5) |
| Physical activity, MET-hr/week | 28.9 (32.6) | 24.3 (27.8) | 26.5 (11.8) |
| Alcohol consumptions, g/d | 6.7 (10.1) | 6.3 (9.6) | 5.7 (10.0) |
| Body mass index, kg/m2 | 26.3 (5.6) | 27.0 (6.0) | 28.6 (6.8) |
| Cumulative night shift work, yrs | 3.2 (4.3) | 3.3 (4.4) | 4.1 (5.1) |
| Usual sleep duration, h/day | |||
| 5 | 4 | 4 | 6 |
| 6 | 20 | 20 | 25 |
| 7 | 40 | 41 | 34 |
| 8 | 30 | 28 | 24 |
| ≥ 9 | 3 | 3 | 6 |
| Post-Menopausal, % | 69 | 68 | 68 |
| Predicted 25-hydroxyvitamin D (ng/ml)2 | 32.0 (4.0) | 32.5 (4.1) | 30.5 (4.1) |
| History of cancer, % | 10 | 9 | 9 |
| History of myocardial infarction, % | 1 | 1 | 1 |
| History of type 2 diabetes, % | 4 | 5 | 8 |
1
Among past and current smokers.
2
Betrand et al. (2012). British Journal of Nutrition, Volume 108(10), pp. 1889–1896.