Table 1.
Descriptive characters of the sample at five waves
| 2004 (T1) | 2006 (T2) | 2009 (T3) | 2011 (T4) | 2015 (T5) | |
|---|---|---|---|---|---|
| Sample size | 3788 | – | – | – | – |
| Focal variable | |||||
| Sleep duration | 8.24 ± 1.34 | 8.15 ± 1.28 | 7.97 ± 1.29 | 7.87 ± 1.26 | 7.81 ± 1.28 |
| < 6 h/day, n(%) | 254 (6.7%) | 293 (7.7%) | 390 (10.3%) | 455 (12.0%) | 483 (12.8%) |
| 6 ~ 7 h/day, n(%) | 639 (16.9%) | 666 (17.6%) | 706 (18.6%) | 753 (19.9%) | 769 (20.3%) |
| 7 ~ 8 h/day, n(%) | 1655 (43.7%) | 1662 (43.9%) | 1771 (46.8%) | 1709 (45.1%) | 1777 (46.9%) |
| ≥ 8 h/day, n(%) | 1240 (32.7%) | 1167 (30.8%) | 921 (24.3%) | 871 (23.0%) | 759 (20.0%) |
| Time-invariant covariates | |||||
| Male, n(%) | 1718 (45.4%) | – | – | – | – |
| Urban residence, n(%) | 1132 (29.9%) | – | – | – | – |
| Age (T1) | 46.72 ± 14.89 | – | – | – | – |
| < 30 years old, n(%) | 357 (9.4%) | – | – | – | – |
| 30 ~ 50 years old, n(%) | 1837 (48.5%) | – | – | – | – |
| ≥ 50 years old, n(%) | 1594 (42.1%) | – | – | – | – |
| BMI (T1) | 23.02 ± 3.59 | – | – | – | – |
| < 18.5 kg/m2, n(%) | 287 (8.1%) | – | – | – | – |
| 18.5 ~ 24 kg/m2, n(%) | 1928 (63.1%) | – | – | – | – |
| ≥ 24 kg/m2, n(%) | 1315 (36.9%) | – | – | – | – |
| Chronic diseases, n(%) | 842 (22.2%) | – | – | – | – |
| Time-varying covariates | |||||
| Smoking, n(%) | 1153 (30.4%) | 1136 (30.0%) | 1115 (29.4%) | 1099 (29.0%) | 943 (24.9%) |
| Alcohol-drinking, n(%) | 1211 (32.0%) | 1207 (31.9%) | 1218 (32.2%) | 1196 (31.6%) | 972 (25.7%) |
T, time; n, sample size; M, mean; SD, standard deviation