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Table 1 Descriptive characters of the sample at five waves

From: Modeling the change trajectory of sleep duration and its associated factors: based on an 11-year longitudinal survey in China

 

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%)

  1. T, time; n, sample size; M, mean; SD, standard deviation